150 lines
6.6 KiB
Plaintext
150 lines
6.6 KiB
Plaintext
|
|
|
|
SAVING DF0: - BOOT UP FROM DF1:
|
|
|
|
by Les Ayling
|
|
|
|
|
|
|||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
|
|
|
|
Several of my friends who are Amiga owners have had problems with the
|
|
internal drive. This modification will overcome that problem by
|
|
allowing Amiga 500 owners to boot from df1:.
|
|
|
|
This mod is also useful for people who own the Commodore 5 1/4 inch
|
|
drives and wish to boot from them. More importantly, people who have
|
|
added an 80trk 5 1/4 inch drive (such as myself) as described in the
|
|
file ADD_5.25_DRIVE can boot from it. As 5 1/4 inch disks can be
|
|
bought for as low as $5.95 for 10 in some places, it is well worth
|
|
considering as a cheap backup library option OR indeed as an
|
|
alternative primary storage medium.
|
|
|
|
You will need the following tools and parts:
|
|
|
|
* Low wattage soldering iron, suitable for PCB's
|
|
* DPDT switch mini toggle variety is fine
|
|
* 1 foot of ribbon cable
|
|
* solder
|
|
* small snippers
|
|
* hand drill
|
|
* tool to unscrew the @#$%^& non-standard case screws
|
|
* Exacto knife or similar
|
|
|
|
Start by unscrewing the 6 hex style screws around the edge of the
|
|
case (Goodbye warranty!). Do not remove the three phillips screws as
|
|
they are holding the drive in place. Turn the machine back the right
|
|
way up and remove the lid by pressing around the edge to ease off the
|
|
catches. Remove the keyboard making careful note of the orientation of
|
|
the connector on the main board!!!!! Now remove the further 4 hex
|
|
screws which are holding the top rf shield in place and remove the
|
|
shield. Unplug the disk drive POWER cable from the drive end only.
|
|
|
|
Remove the 34-way disk drive patch lead taking note of its orientation
|
|
(This saves so much time when you have forgotten later on!) Unscrew
|
|
the Disk drive unit and remove it.
|
|
|
|
The main PC board should now come free with the lower RF shield.
|
|
Unscrew the hexagonal socket retainers on the I/O connectors at the
|
|
rear of the board and this shield should come free.
|
|
|
|
You are now ready to start!
|
|
|
|
Locate connector 11 (CN11) on the component side, this is the socket
|
|
that you just unplugged the disk drive patch lead from. In front of it
|
|
should be U8 which is an 8520 chip.
|
|
|
|
CN11 is 2 rows of 34 pins.Count along the front row from the right
|
|
hand side until you see the 5th and 6th pins (pins 9 and 11 of the
|
|
connector respectively). There should be two circuit traces that lead
|
|
from these pins and disappear under U8. Using the exacto knife cut
|
|
both of these traces leaving no stray copper. A 1mm cut should be
|
|
sufficient.
|
|
|
|
Turn the board over to the solder side.
|
|
Leave the board for a moment and get the DPDT switch.
|
|
For ease I will label its pins as such:
|
|
|
|
A B
|
|
|
|
C D
|
|
|
|
E F
|
|
|
|
Cut a piece of ribbon cable about 1' long with 4 conductors.
|
|
Strip and tin the wires then connect them to A, B, C and D.
|
|
Cut two small pieces of wire and connect A-F and E-B.
|
|
|
|
Tin and strip the other ends of the ribbon cable.Using the snippers
|
|
trim these tinned ends until there is about 1 1/2 to 2mm showing. Any
|
|
longer is unnecessary and can lead to solder blobs etc.
|
|
|
|
Grab the Amiga pc board again. On the solder side locate pins 9 and
|
|
11 of CN11 as described earlier. Solder the lead from A to pin 9 and
|
|
the lead from B to pin 11.
|
|
|
|
Locate pins 13 and 14 of U8.
|
|
|
|
If you are unsure of pin numbering on IC's refer to one of the data
|
|
sections of DSE's or ROD Irving catalogues. Otherwise looking at the
|
|
chip there is a notch at the right hand end of the board. Pin 1 is
|
|
behind this notch (relative to the pc board) and the numbers increase
|
|
in an anti-clockwise fashion around the chip. Solder the lead from C
|
|
to pin 13 of U8 and the lead from D to pin 14 of U8. That completes
|
|
the soldering side of things.
|
|
|
|
All that remains is to drill a hole for the switch and put the rest
|
|
back together. There is a convenient spot to the right of the joystick
|
|
socket that will house 3 or 4 switches comfortably.
|
|
|
|
PLEASE PLEASE PLEASE be careful of the orientation of the connectors
|
|
when assembling your amiga.
|
|
|
|
To use the mod:
|
|
1. Remove ALL disks from ALL drives.
|
|
2. Flick the switch to the NORMAL position.
|
|
3. Turn the machine ON or reset if already ON.
|
|
4. If you wish to boot from drive DF1: now is the time to
|
|
flick the switch to the NON-standard position.
|
|
5. Insert the appropriate disks in the appropriate drives.
|
|
|
|
HOW it works.
|
|
The mod works by switching the drive select lines SEL_0 and SEL_1.
|
|
SIMPLE!
|
|
|
|
IMPORTANT:!!
|
|
The switch must be in the NORMAL position when you either turn the
|
|
machine on or reset.The reason for this is that after a cold or warm
|
|
boot the KERNEL roms go looking for what equipment is connected to the
|
|
system. A part of the GARY chip which is triggered by the SEL_0 signal
|
|
provides seperate MOTOR_ON signals for the internal and external
|
|
drives. When the switch is in the ALTERED position the GARY chip is
|
|
fed by the SEL_1 signal and surprise surprise! the KERNEL roms won't
|
|
find the internal drive! However is is PERFECTLY safe to change the
|
|
switch at ANY time the power is on (without disks in the drives!). So
|
|
if the switch is changed after the roms have found what drives are
|
|
online, the drives 0 and 1 will operate fine only reversed. More
|
|
circuitry could have been added to swap the motor_on signals so that
|
|
this extra switching wasn't required, however most people would
|
|
probably like to keep their mods to the main pcb to a MINIMUM!
|
|
|
|
*NOTE*
|
|
If the switch is changed while disks are inserted in the drives,
|
|
AmigaDOS will become confused as to what volumes are on line and if
|
|
your write-protect tags are OFF, chances are your directories will be
|
|
CLOBBERED!!
|
|
|
|
The mod is relatively simple, however if you are unsure of your
|
|
ability to perform it.. DON'T. get some hardware oriented person to
|
|
help or drop me a line at PARAGON bbs if in Sydney, or via Megadisc and
|
|
I may be able to help or do it for you at a small nominal cost.
|
|
Naturally I cannot guarantee your labour content so therefore I cannot
|
|
make any warranties, implied or otherwise, as to the suitability or
|
|
performance of this modification. However I can say that I am not too
|
|
worried about my software collection as I have a set of bootable 5 1/4"
|
|
backups!!
|
|
|
|
Good luck and I hope that this is of some help.
|
|
|
|
|
|
||||||||||||||||||||||| END OF BOOT_FROM_DF1 ||||||||||||||||||||||||
|