edw@ihlpf.ATT.COM (Ed Windes) (02/09/89)
My father-in-law has a true-blue IBM PC XT with only 256K that he needs to fill out to 640K. What's the easiest way to do this? Are there still memory expansion boards around that will add 384K? Are there any configuration switches on the XT that he'll need to set? thanks, ...att!ihlpf!edw
root@blender.UUCP (Super user) (02/09/89)
In article <7624@ihlpf.ATT.COM>, edw@ihlpf.ATT.COM (Ed Windes) writes: > > My father-in-law has a true-blue IBM PC XT with only 256K > that he needs to fill out to 640K. > > What's the easiest way to do this? > I have several of these motherboards sitting here with only 256K on them. Basically useless. The cost of a 384K expansion (in these parts, calgary) is about $126. The cost of a brand-new 10Mhz 640K ram-less motherboard is $105. In fact, the 384K expansion card is difficult to find since everyone would rather just sell you a new motherboard. -- herb@blender.UUCP "Did I tell you I'm forgetful?"
mvolo@ecsvax.UUCP (Michael R. Volow) (02/11/89)
[deleted stuff about available boards for backfilling IBM PC mother- [Hboard from 256-640K] Don't know exact cost, but must be several boards available, including the ATD Zuckerboard and even the AST SixPackPlus (if you want multi- function). M Volow, VA Medical Center, Durham, N.C. 27705 mvolo@ecsvax.UUCP
NETOPRWA@NCSUVM.BITNET (Wayne Aiken) (02/16/89)
In article <8902151910.AA20013@rti.rti.org>, John DeBoskey asks: >Hello, > Let's backup a second... If you have the true-blue XT motherboard >with 256K memory, you can purchase 2sets of 256k chips, install them >(my board has sockets so this is easy) and make one(1) jumper patch >on the motherboard. Voila, you now have a 640k board. > > John W. De Boskey > >PS: CC to wayne, could you post and/or send this > person the upgrade instructions? I don't have > them anymore. There's been more than one person > ask about this lately... Thanks... ------------------>8------------Cut Here-------------->8--------------------- ** Warning: This procedure involves making direct modifications to your motherboard, and may invalidate any existing warranties. Follow this procedure at your own risk! Technical skills are required and this information is untested as of 9/29/86. Starfleet assumes absolutely NO responsibility for use of this information, although I will gladly post any responses from those who try it. This document describes how to install 640k of RAM on the system board in the IBM XT and the IBM portable (which uses the same mother board). Parts list: Quantity Description --------------------------------------------------------------- 18 256k by 1 dynamic RAM chips (any of the following) Manufacturer Part number ---------------------------------- Fujitsu MB81256-15 Hitachi HM50257-15 Mitsubishi M5M4256-15 NEC uPD41256-15 OKI MSM41256-15 TI TMS4256-15 Toshiba TMM41256-15 1 74LS158 Decoder/multiplexer Integrated circuit Tools required: 1 small flat-head screwdriver 1 small Phillips-head screwdriver 1 soldering iron, low-wattage Rosin-core solder (NOT acid-core) Needle-nose pliers IC chip puller 1 short piece of wire with insulation, stripped on ends IBM XT Instructions: 1. Turn off the system unit, and disconnect the power cables, monitor and keyboard cables and any cables that may be connected to expansion boards. Remove the monitor and the keyboard. Place the system unit in a convenient work area. 2. Take off the cover from the system unit by removing the 5 screws on the back (4 corners and top center), slide the cover forward and tip up to remove completely. 3. Take out any boards installed in the expansion slots by removing the hold down screw at the rear of the chassis, and pulling the card straight up. 4. The floppy disk drives will have to be removed to gain access to portions of the mother board. This is done by removing the screws on the left side of the drive(s). Gently slide the drive(s) out of the unit far enough to get at the cables plugged into the back of them. Making note of where each cable goes, remove the data and power cables by gently pulling them away from the drive. When the cables are off, remove the drive(s) from the chassis and set them aside. 5. Refer to figure 1 and locate the jumper block labeled E2 on the mother board. It is located near the edge of the board near the power supply. 6. A jumper has to be installed between pads 1 and 2 on E2. This can be done without removing the mother board using a short piece of wire. Hold the wire with a pair of needle nose pliers and heat up one of the pads with a soldering iron. When the solder melts, push the wire into the pad and remove the soldering iron. Do the same thing with the other end of the wire and pad. 7. Refer to figure 1 and locate the IC socket labeled U84 on the mother board. This will be an empty socket near the front of the board, underneath where the floppies were mounted. Install the 74LS158 chip in this socket making sure pin 1 (marked with a dot or notch) is pointing away from the front panel. 8. Remove the 64k RAM chips in the rows labeled BANK 0 and BANK 1 (9 in each bank) on the mother board using an IC puller. If you currently only have 128k of memory on the mother board (BANK's 2 and 3 empty) you can move these chips to those banks. Be careful not to damage the pins when removing them (you can sell them to a friend whose machine has amnesia). 9. Install the 256k RAM chips in the now empty sockets of BANK 0 and BANK 1 making sure they are installed correctly with pin 1 pointing away from the front panel. You should now have 2 banks (0 and 1) of 256k RAM chips, and 2 banks (2 and 3) of 64k RAM chips, giving you a total of 640K. 10. Refer to figure 1 and locate the switch block, SW1 on the mother board. Make sure that switch positions 3 and 4 are in the OFF position. 11. Re-install the floppy drive(s) by sliding them into the front panel about half way and reconnect the data and power cables in the same locations they came off of. Push the drive(s) the rest of the way in and anchor them with the screws removed earlier. 12. Re-install your expansion boards (minus any memory boards that used to be in the system) in the reverse order of when you took them out. 13. Put the cover back on, re-connect the cables and install your monitor and keyboard. .----------------------------------------------------------------------. | | | | Expansion | | | Slots | | | | | | | | |--------------------------------------------' | | | | .----------------------------------. | | | BANK 0 | .--. | | `----------------------------------' E |12| | | .----------------------------------. 2 |34| | | | BANK 1 | .-. `--' | | `----------------------------------' |S| | | .----------------------------------. |W| | | | BANK 2 | |1| | | `----------------------------------' `-' | | .----------------------------------. | | | BANK 3 | .-. | | `----------------------------------' |U| | | |8| | | |4| | | `-' | `----------------------------------------------------------------------' Figure 1 (XT/Portable motherboard) --------------------->8----------Cut Here------------------>8---------------- Wayne Aiken netoprwa@ncsuvm.BITNET "Fnord." PO Box 30904 netoprwa@ncsuvm.ncsu.edu Raleigh, NC 27622 StarFleet BBS ---"Bob" (919) 782-8171 (919) 782-3095