96 lines
4.5 KiB
Prolog
96 lines
4.5 KiB
Prolog
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This document describes how to install 640k of RAM on the system board in the
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IBM XT and the IBM portable (which uses the same mother board).
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Parts list:
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Quantity Description
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---------------------------------------------------------------
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18 256k by 1 Dynamic RAM chips (any of the following)
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Manufacturer Part number
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Fujitsu MB81256-15
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Hitachi HM50257-15
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Mitsubishi M5M4256-15
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NEC UPD41256-15
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OKI MSM41256-15
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TI TMS4256-15
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Toshiba TMM41256-15
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1 74LS158 Decoder/multiplexer Integrated circuit
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IBM XT Instructions:
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1. Turn off the system unit, and disconnect the power cables, monitor and
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keyboard cables and any cables that may be connected to expansion boards.
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Remove the monitor and the keyboard. Place the System unit in a convenient
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work area.
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2. Take off the cover from the system unit by removing the 5 screws on the
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back (4 corners and top center), slide the cover forward and tip up to remove
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completely.
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3. Take out any boards installed in the expansion slots by removing the hold
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down screw at the rear of the chassis, and pulling the card straight up.
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4. The floppy disk drives will have to be removed to gain access to portions of
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the mother board. This is done by removing the screws on the left side of the
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drive(s). Gently slide the drive(s) out of the unit far enough to get at the
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cables plugged into the back of them. Making note of where each cable goes,
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remove the data and power cables by gently pulling them away from the drive.
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When the cable are off, remove the drive(s) from the chassis and set them
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aside.
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5. Refer to figure 1 and locate the jumper block labeled E2 on the
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motherboard. It is located near the edge of the board near the power supply.
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6. A jumper has to be installed between pads 1 and 2 on E2. This can be done
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without removing the mother board using a short piece of wire. Hold the wire
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with a pair of needle nose pliers and heat up one of the pads with a soldering
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iron. When the solder melts, push the wire into the pad and remove the
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soldering iron. Do the same thing with the other end of the wire and pad.
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7. Refer to figure 1 and locate the IC socket labeled U84 on the mother board.
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This will be an empty socket near the front of the board, underneath where the
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floppies were mounted. Install the 74LS158 chip in this socket making sure
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pin 1 (marked with a dot or notch) is pointing away from the front panel.
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8. Remove the 64k RAM chips in the rows labeled BANK 0 and BANK 1 (9 in each
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bank) on the mother board using an IC puller. If you currently only have 128k
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of memory on the mother board (BANK's 2 and 3 empty) you can move these chips
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to those banks. Be careful not to damage the pins when removing them (you can
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sell them to a friend whose machine has amnesia).
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9. Install the 256k RAM chips in the now empty sockets of BANK 0 and BANK 1
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making sure they are installed correctly with pin 1 pointing away from the
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front panel. You should now have 2 banks (0 and 1) of 256k RAM chips, and 2
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banks (2 and 3) of 64k RAM chips, giving you a total of 640k.
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10. Refer to figure 1 and locate the switch block, SW1 on the mother board.
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Make sure that switch positions 3 and 4 are in the OFF position.
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11. Re-install the floppy drive(s) by sliding them into the front panel about
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half way and reconnect the data and power cables in the same locations they
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came off of. Push the drive(s) the rest of the way in and anchor them with
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the screws removed earlier.
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12. Re-install the your expansion boards (minus any memory boards that used to
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be in the system) in the reverse order of when you took them out. 13. Put the
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cover back on, re-connect the cables and install your monitor and keyboard.
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------------------------------------------------------------------------
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. EXPANSION
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. SLOTS
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---------------------------------------------
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------------------------------------
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. BANK 0 ----
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------------------------------------ E 12
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------------------------------------ 2 34
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. BANK 1 --- ----
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------------------------------------ S
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------------------------------------ W
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. BANK 2 1
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------------------------------------ ---
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------------------------------------
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. BANK 3 ---
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------------------------------------ U
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. 8
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. 4
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---
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------------------------------------------------------------------------
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Figure 1
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(XT/Portable motherboard)
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