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<20><><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>Ŀ
<20> DIAGRAMS.DOC Supplement to TheRef(tm) Drive & Controller Listing <20><>
<20><><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>Ĵ<EFBFBD>
<20> In "publishing" TheRef(tm), I've often been asked the difference <20><>
<20> between the types of drive controllers and recording methods. I'm <20><>
<20> not going to get into that in this document, as it would require a <20><>
<20> good sized doc. of it's own. What I have supplied are diagrams of <20><>
<20> the different connectors associated with the technology today. <20><>
<20> frf <20><>
<20><><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>Ĵ CABLES <20><><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>Ĵ<EFBFBD>
<20> <20><>
<20> Controller Drive 2(or none) Drive 1 <20><>
<20> <20><>
<20> 1<><31>ͻ <20><><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>1<EFBFBD><31>ͻ <20><><EFBFBD><EFBFBD>stripe<70><65><EFBFBD><EFBFBD><EFBFBD>1<EFBFBD><31>ͻ Pins 10-16 <20><>
<20> FLOPPY cable <20>::<3A><><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>ô<EFBFBD><C3B4><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>ô<EFBFBD> are twisted <20><>
<20> with twist <20>::<3A><><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>ô<EFBFBD><C3B4><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>XX<58><58><EFBFBD>ô<EFBFBD> before the <20><>
<20> (control & <20>::<3A><><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>ô<EFBFBD><C3B4><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>ô<EFBFBD> connector. <20><>
<20> data, 34 pin) <20>::<3A><><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>ô<EFBFBD><C3B4><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>ô<EFBFBD> (7 wires) <20><>
<20> <20><>ͼ <20><>ͼ <20><>ͼ <20><>
<20> 1<><31>ͻ <20><><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>1<EFBFBD><31>ͻ <20><><EFBFBD><EFBFBD>stripe<70><65><EFBFBD><EFBFBD><EFBFBD>1<EFBFBD><31>ͻ Pins 25-29 <20><>
<20> ST412 & ESDI <20>::<3A><><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>ô<EFBFBD><C3B4><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>ô<EFBFBD> are twisted <20><>
<20> Hard Drive <20>::<3A><><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>ô<EFBFBD><C3B4><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>ô<EFBFBD> before the <20><>
<20> cable w/twist <20>::<3A><><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>ô<EFBFBD><C3B4><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>XX<58><58><EFBFBD>ô<EFBFBD> connector. <20><>
<20> (control) <20>::<3A><><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>ô<EFBFBD><C3B4><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>ô<EFBFBD> (5 wires) <20><>
<20> <20><>ͼ <20><>ͼ <20><>ͼ <20><>
<20> 1<><31>ͻ <20><><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>stripe<70><65><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>1<EFBFBD><31>ͻ (no twists) <20><>
<20> ST412 & ESDI <20>::<3A><><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>ô<EFBFBD> Each drive <20><>
<20> Hard Drive <20>::<3A><><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>ô<EFBFBD> has it's <20><>
<20> (data, 20 pin)<29>::<3A><><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>ô<EFBFBD> own data <20><>
<20> <20><>ͼ <20><>ͼ cable <20><>
<20> <20><>
<20> IMPORTANT NOTE: Pin #1 on any drive cable SHOULD be indicated by a <20><>
<20> a colored stripe. If you should find the stripe <20><>
<20> by connector pin 34 (or 20), inspect the whole <20><>
<20> cable VERY throughly! <20><>
<20> <20><>
<20> DRIVE SELECT For both Floppy and Hard drives, when the 34 pin <20><>
<20> JUMPERS: cable has a twist, the device number should be set <20><>
<20> to the second position. Drives numbered 0-3, set to <20><>
<20> 1, those numbered 1-4, set to 2. When cables with- <20><>
<20> out a twist are used, Floppy "A", and(or) Hard drive <20><>
<20> "C" should be set to 1, and the second Floppy and <20><>
<20> (or) Hard drive should be set to 2. <20><>
<20> <20><>
<20> TERMINATORS: When using more than one drive on a cable (ie; 2FDs <20><>
<20> or 2HDs), the terminating resistor pack should be <20><>
<20> left on the drive furthest from the controller, and <20><>
<20> removed from the drive closest to the controller. <20><>
<20> <20><>
<20> NOTE: On SCSI drives, the Host Adapter also has resistors. <20><>
<20> These are needed to terminate both ends of the bus. <20><>
<20> Since the SCSI bus can have up to 7 devices attached <20><>
<20> to it, only the Host Adapter and the device farthest <20><>
<20> from it will retain the resistors. All devices in- <20><>
<20> between should have theirs removed. <20><>
<20><><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>ٱ
<20><><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>
<20><><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>Ŀ
<20> DIAGRAMS.DOC 2 <20><>
<20><><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>Ĵ CONNECTIONS <20><><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>Ĵ<EFBFBD>
<20> <20><>
<20> FLOPPY DRIVES <20><><EFBFBD><EFBFBD><EFBFBD>Ŀ <20><>
<20> HI/LO DENSITY ><3E>2 1<> GND <20><>
<20> The connector on a floppy drive N/C <20>4 _ 3<> | <20><>
<20> consists of 34 conductors. Both N/C <20>6 5<> | <20><>
<20> control and data use this same INDEX <<3C>8 7<> | <20><>
<20> cable. Most cables have a twist MOTOR ENAB. A ><3E>10 9<> | <20><>
<20> that interchanges pins 10 through DRIVE SEL. B ><3E>12 11<31> | <20><>
<20> 16 at the end of the cable (on DRIVE SEL. A ><3E>14 13<31> | <20><>
<20> drive 1). Most floppy connect- MOTOR ENAB. B ><3E>16 15<31> | <20><>
<20> ors have a "key" between pins DIRECTION SEL. ><3E>18 17<31> | <20><>
<20> 4 & 6, and 3 & 5, to prevent the HEAD STEP ><3E>20 19<31> | <20><>
<20> cable from being reversed. At WRITE DATA ><3E>22 21<32> | <20><>
<20> the other end, the dual row con- WRITE GATE ><3E>24 23<32> | <20><>
<20> nector that attaches to the con- TRACK 00 <<3C>26 25<32> | <20><>
<20> troller card will usually have a WRITE PROTECT <<3C>28 27<32> | <20><>
<20> set of ridges that coincide with READ DATA <<3C>30 29<32> | <20><>
<20> cutouts in the controller card's HEAD SELECT ><3E>32 31<33> | <20><>
<20> connector. Note that old style DISK CHANGE <<3C>34 33<33> GND <20><>
<20> floppy-only controllers used a <20><><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD> <20><>
<20> card-edge connector just like that > Input ( At the <20><>
<20> of the drive. < Output Drive Conn.) <20><>
<20> <20><>
<20> ST506/412 HARD DRIVE (MFM & RLL) <20><>
<20> <20><>
<20> This standard drive system uses <20><><EFBFBD><EFBFBD><EFBFBD>Ŀ <20><>
<20> two cables; a 34 conductor control HEAD SEL. 8 <20>2 1<> GND <20><>
<20> cable, and a 20 conductor data HEAD SEL. 4 <20>4 _ 3<> | <20><>
<20> cable. The control cable contains WRITE GATE <20>6 5<> | <20><>
<20> a twist of the conductors going to SEEK COMPLETE <20>8 7<> | <20><>
<20> the farthest drive, which is drive TRACK 0 <20>10 9<> | <20><>
<20> "C" on most systems. This twist WRITE FAULT <20>12 11<31> | <20><>
<20> consists of conductors 25 through HEAD SEL. 1 <20>14 13<31> | <20><>
<20> 29. As with the floppy cable, the RESERVED <20>16 15<31> | <20><>
<20> ST506/412 cables normally have a HEAD SEL. 2 <20>18 17<31> | <20><>
<20> key to prevent reversal, and the INDEX <20>20 19<31> | <20><>
<20> controller end has a pin-type con- READY <20>22 21<32> | <20><>
<20> nector, while the drive end has a STEP <20>24 23<32> | <20><>
<20> card-edge type connector. DRIVE SEL. 1 <20>26 25<32> | <20><>
<20> DRIVE SEL. 2 <20>28 27<32> | <20><>
<20> <20><><EFBFBD><EFBFBD><EFBFBD>Ŀ DRIVE SEL. 3 <20>30 29<32> | <20><>
<20> DRIVE SEL'D <20>1 2<> GND DRIVE SEL. 4 <20>32 31<33> | <20><>
<20> RESERVED <20>3 _ 4<> | DIRECTION IN <20>34 33<33> GND <20><>
<20> | <20>5 6<> | <20><><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD> <20><>
<20> | <20>7 8<> GND <20><>
<20> RESERVED <20>9 10<31> RESERVED Though control signals <20><>
<20> GND <20>11 12<31> GND go through a single 34 <20><>
<20> * WRITE DATA+ <20>13 14<31> * WRITE DATA- conductor cable, data <20><>
<20> GND <20>15 16<31> GND flows through seperate <20><>
<20> * READ DATA+ <20>17 18<31> * READ DATA- 20 conductor cables <20><>
<20> GND <20>19 20<32> GND for each drive (C,D). <20><>
<20> *(MFM or RLL) <20><><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD> <20><>
<20><><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>ٱ
<20><><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>
<20><><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>Ŀ
<20> DIAGRAMS.DOC 3 <20><>
<20><><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>Ĵ CONNECTIONS <20><><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>Ĵ<EFBFBD>
<20> <20><>
<20> ESDI HARD DRIVES <20><><EFBFBD><EFBFBD><EFBFBD>Ŀ <20><>
<20> HEAD SEL. 3 <20>2 1<> GND <20><>
<20> Though ESDI and ST506/412 drives HEAD SEL. 2 <20>4 _ 3<> | <20><>
<20> share similar looking cables, WRITE GATE <20>6 5<> | <20><>
<20> even to the point of having a CONFIG/STAT DATA <20>8 7<> | <20><>
<20> twist, the actual data and con- TRANSFER ACK. <20>10 9<> | <20><>
<20> trol signals are very different. ATTENTION <20>12 11<31> | <20><>
<20> One should never mix components HEAD SEL. 0 <20>14 13<31> | <20><>
<20> from these two drive types. SECT/ADD.MK. FOUND <20>16 15<31> | <20><>
<20> While the ST506/412 interface HEAD SEL. 1 <20>18 17<31> | <20><>
<20> utilizes a standard pulse code INDEX <20>20 19<31> | <20><>
<20> to transmit data between the READY <20>22 21<32> | <20><>
<20> drive and controller, ESDI uses TRANS.REQUEST <20>24 23<32> | <20><>
<20> a pulse code that does not require DRIVE SEL. 1 <20>26 25<32> | <20><>
<20> the level to return to zero between DRIVE SEL. 2 <20>28 27<32> | <20><>
<20> pulses. This format is refered to DRIVE SEL. 3 <20>30 29<32> | <20><>
<20> as NRZ, or Non Return to Zero. By READ GATE <20>32 31<33> | <20><>
<20> utilizing NRZ, the clock that data COMMAND DATA <20>34 33<33> GND <20><>
<20> is transfered by can be increased, <20><><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD> <20><>
<20> thereby increasing the troughput to <20><>
<20> and from the ESDI disk. <20><>
<20> <20><><EFBFBD><EFBFBD><EFBFBD>Ŀ <20><>
<20> DRIVE SEL'D <20>1 2<> SECT/ADD.MK. FOUND <20><>
<20> SEEK COMPLETE <20>3 _ 4<> ADDRESS MARK ENABLE <20><>
<20> RESV'D FOR STEP MODE <20>5 6<> GND <20><>
<20> WRITE CLOCK+ <20>7 8<> WRITE CLOCK- <20><>
<20> CARTRIDGE CHANGED <20>9 10<31> READ REF. CLOCK+ <20><>
<20> READ REF. CLOCK- <20>11 12<31> GND <20><>
<20> NRZ WRITE DATA+ <20>13 14<31> NRZ WRITE DATA- <20><>
<20> GND <20>15 16<31> GND <20><>
<20> NRZ READ DATA+ <20>17 18<31> NRZ READ DATA- <20><>
<20> GND <20>19 20<32> GND <20><>
<20> <20><><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD> <20><>
<20> <20><>
<20> <20><><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>Ŀ And in this corner... Recording <20><><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD> <20><>
<20> <20><>
<20> Times were, you had a simple choice for type of disk drive... <20><>
<20> Any kind, as long as it was ST506/412. Those were the heydays of <20><>
<20> MFM drives. But many manufacturers weren't content with the 17 <20><>
<20> sectors/track that MFM provided. They devised a newer encoding <20><>
<20> scheme to pack data tighter, and called it RLL, or Run Length <20><>
<20> Limited, as opposed to MFM, or Modified Frequency Modulation. It <20><>
<20> involves using groups of 16 bits rather than each individual bit, <20><>
<20> thus achieving a sort of "compression" of the information as it is <20><>
<20> encoded. Since the same information takes up less space as RLL <20><>
<20> encoded data, more info can be writen to the disk. The most com- <20><>
<20> mon RLL technique, known as 2,7 RLL, can pack roughly 50% more on <20><>
<20> a disk than MFM. Of course, there is always a trade-off, and the <20><>
<20> timing and media required for RLL is it. RLL requires a higher <20><>
<20> grade of media because of it's dense bit-packing, and timing is <20><>
<20> more critical, since the data is flowing at 50% higher rate than <20><>
<20> an MFM drive. Also, the mechanics of the drive must have tighter <20><>
<20><><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>ٱ
<20><><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>
<20><><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>Ŀ
<20> DIAGRAMS.DOC 4 <20><>
<20><><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>Ĵ<EFBFBD>
<20> tolerences because head positioning becomes more critical. These <20><>
<20> requirements kept RLL drives at a premium. It has only been the <20><>
<20> last two years, that RLL drives have outsold MFM, and have all but <20><>
<20> wiped them from the marketplace. This turnabout has come from the <20><>
<20> need to increase disk capacity more and more. Both ESDI, and SCSI <20><>
<20> type drives utilize RLL.(1*) encoding to achieve high capacity and <20><>
<20> transfer rates (from the disk). And the newest interface, IDE, or <20><>
<20> Integrated Drive Electronics, is also based on this technology. <20><>
<20> <20><><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>Ŀ <20><><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD> <20><>
<20> <20><><EFBFBD><EFBFBD><EFBFBD>Ŀ <20><>
<20> SCSI HARD DRIVES DB0 <><3E>2 1<> GND 5 <20><>
<20> DB1 <><3E>4 3<> | 0 <20><>
<20> The normal internal cable for SCSI DB2 <><3E>6 5<> | <20><>
<20> is a 50 conductor ribbon, with all DB3 <><3E>8 7<> | P <20><>
<20> odd numbered conductors grounded. DB4 <><3E>10 9<> | I <20><>
<20> Two conductors, numbers 25 & 26, are DB5 <><3E>12 11<31> | N <20><>
<20> often left not-connected, as they DB6 <><3E>14 13<31> | <20><>
<20> deal with Terminator power, and can DB7 <><3E>16 15<31> | D <20><>
<20> be easily shorted by cable reversals. DBP <><3E>18 17<31> | U <20><>
<20> There are no twists in this cable, GND <20>20 19<31> | A <20><>
<20> and it's length may be a maximum of GND <20>22 21<32> | L <20><>
<20> 6 meters. But one is advised to use GND <20>24 23<32> | <20><>
<20> minimum lengths to improve timing. TERM PWR <20>26 25<32> | R <20><>
<20> Up to seven drives, or devices may be GND <20>28 27<32> | O <20><>
<20> attached to an SCSI cable. Each is GND <20>30 29<32> | W <20><>
<20> daisy-chained on the cable, or, when ATN < <20>32 31<33> | <20><>
<20> a device has two connectors, another GND <20>34 33<33> | C <20><>
<20> cable may be "spliced" into the chain BSY <><3E>36 35<33> | O <20><>
<20> starting at the second connector, and ACK < <20>38 37<33> | N <20><>
<20> continued on. Care must be taken to RST <><3E>40 39<33> | N <20><>
<20> insure that cables and connectors are MSG ><3E>42 41<34> | E <20><>
<20> not reversed, as this would short pin SEL <><3E>44 43<34> | C <20><>
<20> 26 (TERMPWR) to ground, and likely C/D ><3E>46 45<34> | T <20><>
<20> damage the drive or controller. Also, REQ ><3E>48 47<34> | O <20><>
<20> as explained earlier, the terminating I/O ><3E>50 49<34> GND R <20><>
<20> resistors should remain only on the <20><><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD> <20><>
<20> controller (Host Adapter) and the LAST <20><>Ŀ DB-25F CONN. <20><>
<20> drive on the cable, regardless of it's GND <20>1 <20><>Ŀ <20><>
<20> address. DB1 <><3E>2 14<31><> DB0 <20><>
<20> Most SCSI Host Adapters also have DB3 <><3E>3 15<31><> DB2 <20><>
<20> a connector for external drives in the DB5 <><3E>4 16<31><> DB4 <20><>
<20> form of a Centronics(tm) type 50 pin, DB7 <><3E>5 17<31><> DB6 <20><>
<20> or an "alternate", DB-25F connector. GND <20>6 18<31><> PARITY <20><>
<20> Only the internal 50-pin, and the SEL <><3E>7 19<31> GND <20><>
<20> "alternate" external connector are GND <20>8 20<32> > ATN <20><>
<20> shown here. (see also: MORE SCSI) TMPWR <20>9 21<32>< MSG <20><>
<20> Also, these diagrams refer to the RST <><3E>10 22<32> > ACK <20><>
<20> single-ended SCSI connections, since C/D <20>11 23<32><> BSY <20><>
<20> this is the most common arrangement I/O ><3E>12 24<32>< REQ <20><>
<20> for PCs today. The Differential SCSI GND <20>13 25<32> GND <20><>
<20> requires balanced lines, and is used <20> <20><><EFBFBD><EFBFBD> <20><>
<20> mostly on high-end workstations. <20><><EFBFBD><EFBFBD> FUTURE DOMAIN<49><4E>
<20><><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>ٱ
<20><><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>
<20><><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>Ŀ
<20> DIAGRAMS.DOC 5 <20><>
<20><><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>Ĵ CABLES <20><><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>Ĵ<EFBFBD>
<20> SCSI (cont.) <20><>
<20> (T) <20><>(DC)<29> (T) <20><>
<20> On an SCSI cable, the 1<><31>ͻ<EFBFBD>stripe<70>1<EFBFBD><31>ͻ<EFBFBD><CDBB>1<EFBFBD><31>ͻ<EFBFBD><CDBB>1<EFBFBD><31><EFBFBD><EFBFBD><EFBFBD>ͻ<EFBFBD><CDBB>1<EFBFBD><31>ͻ <20><>
<20> terminating resistors <20>::<3A><><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>::<3A><><EFBFBD><EFBFBD><EFBFBD>::<3A><><EFBFBD><EFBFBD><EFBFBD>::<3A>::<3A><><EFBFBD><EFBFBD><EFBFBD>::<3A> <20><>
<20> (T) remain at the END <20>::<3A><><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>::<3A><><EFBFBD><EFBFBD><EFBFBD>::<3A><><EFBFBD><EFBFBD><EFBFBD>::<3A>::<3A><><EFBFBD><EFBFBD><EFBFBD>::<3A> <20><>
<20> devices on the cable, <20>::<3A><><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>::<3A><><EFBFBD><EFBFBD><EFBFBD>::<3A><><EFBFBD><EFBFBD><EFBFBD>::<3A>::<3A><><EFBFBD><EFBFBD><EFBFBD>::<3A> <20><>
<20> even when 2 cables are <20>::<3A><><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>::<3A><><EFBFBD><EFBFBD><EFBFBD>::<3A><><EFBFBD><EFBFBD><EFBFBD>::<3A>::<3A><><EFBFBD><EFBFBD><EFBFBD>::<3A> <20><>
<20> "Daisy-Chained" (DC). <20>::<3A><><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>::<3A><><EFBFBD><EFBFBD><EFBFBD>::<3A><><EFBFBD><EFBFBD><EFBFBD>::<3A>::<3A><><EFBFBD><EFBFBD><EFBFBD>::<3A> <20><>
<20> Also, the external <20>::<3A><><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>::<3A><><EFBFBD><EFBFBD><EFBFBD>::<3A><><EFBFBD><EFBFBD><EFBFBD>::<3A>::<3A><><EFBFBD><EFBFBD><EFBFBD>::<3A> <20><>
<20> connector may be used, <20><>ͼ <20><>ͼ <20><>ͼ <20><><EFBFBD><EFBFBD><EFBFBD>ͼ <20><>ͼ <20><>
<20> requiring the removal (HA) Drives 1-7 (in any order) <20><>
<20> of the Host Adapter's <20><>
<20> internal Term. resistors. <20><>
<20><><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>Ĵ CONNECTORS <20><><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>Ĵ<EFBFBD>
<20> <20><>
<20> IDE (AT) HARD DRIVES (<> AT THE DRIVE CONN) <20><>
<20> <20><><EFBFBD><EFBFBD><EFBFBD>Ŀ <20><>
<20> IDE, or Integrated Drive Electronics RST ><3E>1 2<> GND <20><>
<20> is the most recent drive interface to SD7 <><3E>3 4<><> SD8 <20><>
<20> gain popularity. Often, the control SD6 <><3E>5 6<><> SD9 <20><>
<20> circuitry is built into the mother- SD5 <><3E>7 8<><> SD10 <20><>
<20> board, eliminating the requirement for SD4 <><3E>9 10<31><> SD11 <20><>
<20> a seperate Host Adapter. There are 2 SD3 <><3E>11 12<31><> SD12 <20><>
<20> types of IDE interfaces...those for the SD2 <><3E>13 14<31><> SD13 <20><>
<20> 8-bit XT bus, and those for the 16-bit SD1 <><3E>15 16<31><> SD14 <20><>
<20> AT bus (detailed here). The cable for SD0 <><3E>17 18<31><> SD15 <20><>
<20> IDE contains 40 conductors and has no GND <20>19 20<32>N/C (KEY) <20><>
<20> twists. Like an SCSI cable, the IDE RES.N/C<>21 22<32> GND <20><>
<20> cable uses a Dual-row Pin connector for IOW ><3E>23 24<32> GND <20><>
<20> both ends. A single cable may be used IOR ><3E>25 26<32> GND <20><>
<20> to connect two drives, or two cables RES.N/C<>27 28<32>N/C RES. <20><>
<20> may be Daisy-Chained. Most IDE Host RES.N/C<>29 30<33> GND <20><>
<20> Adapters will support two hard drives. IRQ14 <<3C>31 32<33>> I/O CS16 <20><>
<20> The first drive should be jumpered as SA1 <><3E>33 34<33><> PDIAG <20><>
<20> the Master drive, and the second as the SA0 <><3E>35 36<33><> SA2 <20><>
<20> Slave drive. Plug-in IDE Host Adapters CS0 ><3E>37 38<33>< CS1 <20><>
<20> are often called Paddle-Boards, and ACTIVE <<3C>39 40<34> GND <20><>
<20> may contain a floppy controller, and <20><><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD> <20><>
<20> serial and parallel ports. <20><>
<20> <20><>
<20><><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>Ĵ CABLES <20><><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>Ĵ<EFBFBD>
<20> Note: <20><>
<20> 1<><31>ͻ<EFBFBD><CDBB><EFBFBD><EFBFBD>stripe<70><65><EFBFBD><EFBFBD><EFBFBD>1<EFBFBD><31>ͻ<EFBFBD><CDBB><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>1<EFBFBD><31>ͻ <20><>
<20> The IDE Host Adapter <20>::<3A><><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>::<3A><><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>::<3A> <20><>
<20> connector may be on <20>::<3A><><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>::<3A><><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>::<3A> <20><>
<20> a plug-in Paddle-Board <20>::<3A><><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>::<3A><><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>::<3A> <20><>
<20> or may be integrated <20>::<3A><><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>::<3A><><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>::<3A> <20><>
<20> on the Motherboard. <20>::<3A><><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>::<3A><><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>::<3A> <20><>
<20> <20><>ͼ <20><>ͼ <20><>ͼ <20><>
<20> Host Adapter Drives 1-2 (any order) <20><>
<20><><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>Ĵ<EFBFBD>
<20> 1* There ARE some SCSI drives that utilize MFM, but very few. <20><>
<20><><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>ٱ
<20><><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>
<20><><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>Ŀ
<20> DIAGRAMS.DOC 6 <20><>
<20><><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>Ŀ More on Recording <20><><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>Ĵ<EFBFBD>
<20> <20><>
<20> WRITE PRECOMPENSATION <20><>
<20> <20><>
<20> OK, so we've all seen it listed, and maybe even had to set it <20><>
<20> in the CMOS. So what IS it? And what does it do? <20><>
<20> PreComp. is the way in which the electronics compensates for <20><>
<20> eventual "drift" of the magnetic domains written on the disk. A <20><>
<20> simple explaination is that it allows the head to space bits that <20><>
<20> would attract each other, further apart, while it puts those that <20><>
<20> repel each other, closer together. It does this by analyzing the <20><>
<20> data stream, and adjusting the timing for each bit, to allow it to <20><>
<20> be recorded earlier or later, if needed. <20><>
<20> Not all disks require you to set their PreComp value. Those <20><>
<20> that do are asking for a cylinder to start PreComp. at. Since the <20><>
<20> packing of the bits on a disk increases as you get closer to the <20><>
<20> center of the disk (higher cylinders), the requirement for PreComp.<2E><>
<20> increases too. The PreComp. value specified by the Manufacturer <20><>
<20> for a disk is his way of insuring your long term data stability. <20><>
<20> <20><>
<20> <20><>< THE EFFECT OF PRECOMPENSATION OVER TIME ><3E><> <20><>
<20> <20><>
<20> When recorded (w/o PreComp) When recorded (with PreComp) <20><>
<20> <20><><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>Ŀ <20><><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>Ŀ <20><>
<20> <20> +- -+ +- +- -+ -+ <20> <20> +- -+ +- -+ -+ -+<2B> <20><>
<20> <20><><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD> <20><><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD> <20><>
<20> <20><>
<20> After time (w/o PreComp) After time (with PreComp) <20><>
<20> <20><><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>Ŀ <20><><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>Ŀ <20><>
<20> <20>+- -+ +- +- -+ -+ <20> <20> +- -+ +- -+ -+ -+ <20> <20><>
<20> <20><><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD> <20><><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD> <20><>
<20> <20><>
<20> From the figures above, we can see how a slight amount of Pre- <20><>
<20> Compensation can insure long term stability. The disk that didn't <20><>
<20> employ PreComp was eventually unreadable. Of course, this would <20><>
<20> take time to happen, but no one can give cold hard specs on how <20><>
<20> much drift will occure. (Of course, this example is a gross sim- <20><>
<20> plification of the process, but, hey, who's counting?) <20><>
<20> <20><>
<20><><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>Ĵ For Notes & Such <20><><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>Ĵ<EFBFBD>
<20> <20><>
<20> <20><>
<20> <20><>
<20> <20><>
<20> <20><>
<20> <20><>
<20> <20><>
<20> <20><>
<20> <20><>
<20> <20><>
<20> <20><>
<20> <20><>
<20> <20><>
<20><><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>ٱ
<20><><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>
<20><><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>Ŀ
<20> DIAGRAMS.DOC 7 <20><>
<20><><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>Ĵ<EFBFBD>
<20> APPLE SCSI <20><>
<20> <20><>
<20> Unlike in the PC world, the Apple APPLE DB-25 SCSI <20><>
<20> standardized on one drive interface, <20><><EFBFBD><EFBFBD>Ŀ <20><>
<20> SCSI. Also, Apple standardized on REQ ><3E>1 <20><> <20><>
<20> a 25 pin connector for external con- MSG ><3E>2 14<31> GND <20><>
<20> nections. However, Apple decided not I/O ><3E>3 15<31>< C/D <20><>
<20> to implement the complete ANSI spec., RST <><3E>4 16<31> GND <20><>
<20> so one must be careful that peripherals ACK < <20>5 17<31> > ATN <20><>
<20> used are certified to work with Apple's BSY <><3E>6 18<31> GND <20><>
<20> SCSI bus. GND <20>7 19<31><> SEL <20><>
<20> Apple also developed it's own pin- DB0 <><3E>8 20<32><> PARITY <20><>
<20> configuration. The Apple and Future GND <20>9 21<32><> DB1 <20><>
<20> Domain 25-pin SCSI connectors are as DB3 <><3E>10 22<32><> DB2 <20><>
<20> close to "Standards" as there are in DB5 <><3E>11 23<32><> DB4 <20><>
<20> the world of PCs. But the real ANSI DB6 <><3E>12 24<32> GND <20><>
<20> Standard called for a 50 pin connector DB7 <><3E>13 25<32> TMPWR <20><>
<20> commonly referred to as a "Centronics" <20> <20><> <20><>
<20> type (made popular by the Centronics <20><><EFBFBD><EFBFBD><EFBFBD><EFBFBD> <20><>
<20> printer company). Instead of the 25 <20><>
<20> staggered pins of the Apple & Future <20><>
<20> Domain type connectors, the Centronics <20><><EFBFBD>Ŀ <20><>
<20> type uses 2 parallel rows of 25 pins. <20> <20>Ŀ <20><>
<20> This arrangement allows the use of extra GND <20>1 26<32><> DB0 <20><>
<20> grounds for better isolation. <20> <20>2 27<32><> DB1 <20><>
<20> <20> <20>3 28<32><> DB2 <20><>
<20> SCSI HISTORY <20> <20>4 29<32><> DB3 <20><>
<20> <20> <20>5 30<33><> DB4 <20><>
<20> SCSI has it's roots in the mainframe <20> <20>6 31<33><> DB5 <20><>
<20> world, but it's first implementation in <20> <20>7 32<33><> DB6 <20><>
<20> the PC world came soon after the first <20> <20>8 33<33><> DB7 <20><>
<20> PC. Shugart Associates devised an inter- <20> <20>9 34<33><> DBP <20><>
<20> face that they designated the SASI, or <20> <20>10 35<33> GND <20><>
<20> "Shugart Associates Standard Interface" <20> <20>11 36<33> GND <20><>
<20> They proposed that SASI be adopted by ANSI <20> <20>12 37<33> GND <20><>
<20> for small computers, but durring the work <20> <20>13 38<33> TERM.PWR. <20><>
<20> required for ratification, they discovered <20> <20>14 39<33> GND <20><>
<20> the process would take too much effort, and <20> <20>15 40<34> GND <20><>
<20> that the IPI groups were already well into <20> <20>16 41<34> > ATN <20><>
<20> their effort. (which had many features the <20> <20>17 42<34> GND <20><>
<20> same as SASI) A decision was made to take <20> <20>18 43<34><> BSY <20><>
<20> features of both interfaces, and put forth <20> <20>19 44<34> > ACK <20><>
<20> a new specification for a new interface, <20> <20>20 45<34><> RST <20><>
<20> SCSI was born, and ratified in 1986 by <20> <20>21 46<34>< MSG <20><>
<20> ANSI. Since then, many have said that the <20> <20>22 47<34><> SEL <20><>
<20> original spec. was not tight enough, and <20> <20>23 48<34>< C/D <20><>
<20> that it allowed Manufacturers to make <20> <20>24 49<34>< REQ <20><>
<20> drives that met the ANSI spec., but would GND <20>25 50<35>< I/O <20><>
<20> not talk to each other. Recently, the <20> <20><><EFBFBD> <20><>
<20> ANSI SCSI committee has proposed newer, <20><><EFBFBD><EFBFBD><EFBFBD> <20><>
<20> tighter, more extended specs., for 50 PIN "CENTRONICS" <20><>
<20> SCSI-2, and now SCSI-3. FOR "PC" TYPE COMPUTERS <20><>
<20><><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>ٱ
<20><><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>
<20><><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>Ŀ
<20> DIAGRAMS.DOC 8 <20><>
<20><><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>Ŀ CONSTRUCTION PROJECT <20><><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>Ĵ<EFBFBD>
<20> SCSI TERMINATION <20><>
<20> <20><>
<20> With the advent of increased use of SCSI for peripherals comes <20><>
<20> the chance that one day you'll need an SCSI terminating resistor. <20><>
<20> Prepare for a shock, because you might be very suprised at the <20><>
<20> prices charged, for what you get. Many Manufacturers still have <20><>
<20> SCSI peripheral hardware priced <20><><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>Ŀ <20><>
<20> for the Workstation market, not <20> 1 <20>/\/\/\/<2F> 26 <20>/\/\/\/Ŀ <20> <20><>
<20> the PC market. We may see these <20> 2 <20>/\/\/\/<2F> 27 <20>/\/\/\/Ĵ <20> <20><>
<20> prices erode as more PCs adopt <20> 3 <20>/\/\/\/<2F> 28 <20>/\/\/\/Ĵ <20> <20><>
<20> SCSI as their disk interface of <20> 4 <20>/\/\/\/<2F> 29 <20>/\/\/\/Ĵ <20> <20><>
<20> choice, but for now be prepared <20> 5 <20>/\/\/\/<2F> 30 <20>/\/\/\/Ĵ <20> <20><>
<20> to pay a premium for anything to <20> 6 <20>/\/\/\/<2F> 31 <20>/\/\/\/Ĵ <20> <20><>
<20> do with SCSI. <20> 7 <20>/\/\/\/<2F> 32 <20>/\/\/\/Ĵ <20> <20><>
<20> So here you are, with a disk <20> 8 <20>/\/\/\/<2F> 33 <20>/\/\/\/Ĵ <20> <20><>
<20> drive mounted internally, and a <20> 9 <20>/\/\/\/<2F> 34 <20>/\/\/\/Ĵ <20> <20><>
<20> CDRom hanging off the back of the <20> 10 35 <20> <20> <20><>
<20> PC. Everything looks great, but <20> 11 36 <20> <20> <20><>
<20> it just doesn't work... Maybe it <20> 12 37 <20> <20> <20><>
<20> doesn't even recognize the CDRom. <20> 13 38 <20><><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>Ĵ <20> <20><>
<20> You've checked the connectors, and<6E> 14 39 <20> <20> <20><>
<20> everything looks good... So what's<> 15 40 <20> <20> <20><>
<20> the problem? Well, did you check <20> 16 <20>/\/\/\/<2F> 41 <20>/\/\/\/Ĵ <20> <20><>
<20> the terminators? (Say Whaaat??) <20> 17 42 <20> <20> <20><>
<20> Improper termination of an SCSI <20> 18 <20>/\/\/\/<2F> 43 <20>/\/\/\/Ĵ <20> <20><>
<20> bus can raise havock with the Host<73> 19 <20>/\/\/\/<2F> 44 <20>/\/\/\/Ĵ <20> <20><>
<20> Adapter's interface circuit, and <20> 20 <20>/\/\/\/<2F> 45 <20>/\/\/\/Ĵ <20> <20><>
<20> result in missing peripherals, or <20> 21 <20>/\/\/\/<2F> 46 <20>/\/\/\/Ĵ <20> <20><>
<20> intermittent operation and pos- <20> 22 <20>/\/\/\/<2F> 47 <20>/\/\/\/Ĵ <20> <20><>
<20> sible loss of data. <20> 23 <20>/\/\/\/<2F> 48 <20>/\/\/\/Ĵ <20> <20><>
<20> Well, here's a way to build an <20> 24 <20>/\/\/\/<2F> 49 <20>/\/\/\/Ĵ <20> <20><>
<20> inexpensive terminator that will <20> 25 <20>/\/\/\/<2F> 50 <20>/\/\/\/<2F><> <20> <20><>
<20> connect to the second SCSI con- <20> 220<32> 330<33> <20> <20><>
<20> nector on many SCSI peripherals. <20><><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD> <20><>
<20> All you need is a Male 50-pin SCSI Terminator Schematic <20><>
<20> Centronics type connector, a small <20><>
<20> length of wire, and 18 resistors of 330<33> and 18 of 220<32>, 1/4 watt. <20><>
<20> The schematic for connecting the resistors & connector is above, <20><>
<20> and I'll not go any deeper into construction except to say that if <20><>
<20> you can't take it from here without explaination, you should buy <20><>
<20> your terminator instead, as you can do too much damage if you do it<69><74>
<20> wrong. <20><>
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