C08926RC@WUVMD.WUSTL.EDU (Rob Caton) (11/01/90)
I recently required a genuine IBM XT motherboard with 0k. The date on the BIOS chip is 1986 and elsewhere on the board it says 256 - 640k. My question is twofold: can this board be populated with 640k using 256x1 and 64x1 chips, and if so, what are the proper dipswitch settings? The reason I ask the list is because a local service tech told me that all true IBM XT boards have 128k soldered on board and 3 empty banks which used 128k piggyback chips to give a total of 512k. He also said that the board probably had 256 - 64k written on it instead of the above - he didnt see the board. The board I have has 4 empty banks and no soldered memory. Thanks for any help! |==================================================================| | Rob Caton | | Disclaimer: | | Programmer/Analyst | "I live with danger | What? | | Washington University | everyday, J. R., | Me worry? | |-------------------------| but occasionally I |-----------------| | C08926RC@WUVMD | leave her and go hunting."--GABI | |==================================================================|
v087mxgb@ubvmsa.cc.buffalo.edu (Shawn E Thompson) (11/01/90)
>is twofold: can this board be populated with 640k using 256x1 and 64x1 >chips, and if so, what are the proper dipswitch settings? >| Washington University | everyday, J. R., | Me worry? | Quoting from IBM's 'Technical Reference Manual: Personal Computer XT and Portable Personal Computer' (IBM manual #6322508); " RAM The system board also has from 128K by 9 to 256K by 9 of R/W memory. A minimum system would have 128K of memeory, with module sockets for an additional 128K. Memory greater than the system board's maximum of 256K is obtained by adding memory cards in the expansion slots. The memory consists of dynamic 64K by 1 chips with an access time of 200-ns and a cycle time of 345-ns. All R/W memory is parity checked." This manual refers the user to the 'Guide to Operations: Personal Computer XT" for dipswitch settings, which consists of FIFTEEN pages of switch settings (the eight switch block on the system board is as follows: switch #1 ALWAYS OFF!! switch #2 math coprocessor (yes or no) switch #3 & #4 on board RAM (off-on=128K,on-off=192K,off-off=256K) system board must be fully populated before you can add a memory expansion option. switch #5 & #6 graphics adaptor (off-on=CGA in 40x25 mode, on-off=CGA in 80x25 mode, off-off=monochrome, on-on=no display) switch #7 & #8 drives (on-on = 1 floppy, off-on=2 floppies) The remainder of RAM options are set with switch blocks on the RAM expansion cards (TWELVE pages of settings). I use an Inboard and/or above board (depending on which system), and have 1280K addressable RAM - works very well. Shawn E. Thompson "..my sig file was so long, I'm not even allowed a quote..." v087mxgb@ubvms.cc.buffalo.edu | set@autarch.acsu.buffalo.edu University @ Buffalo|Graduate School of Mechanical Engineering CAD Engineering|Leica, Inc.|PO Box 123|Buffalo, NY 14240-0123|(716)891-3375
BEEBE@YALEMED.BITNET (Rick Beebe) (11/02/90)
>From: Rob Caton <C08926RC@WUVMD.Wustl.Edu> > >I recently required a genuine IBM XT motherboard with 0k. The date on the >BIOS chip is 1986 and elsewhere on the board it says 256 - 640k. My question >is twofold: can this board be populated with 640k using 256x1 and 64x1 >chips, and if so, what are the proper dipswitch settings? The answer is Yes and I don't know. Sorry. Near the end of their life, IBM switched to a 640K motherboard for XT's. I myself have only seen one, and I'm afraid I don't have any docs on them. Your service rep (who said all true IBM XT boards have 256 - 64k written on them) has probably never seen one. ----------------------------------------------------------------------------- Rick Beebe (203) 785-4566 ***** ***** ***** * * Biomedical Computing Unit * * * ** * Yale University School of Medicine * * *** * * * 333 Cedar Street, New Haven, CT 06514 * * * * ** * * * * * BEEBE@YALEMED.BITNET beebe%biomed.decnet@venus.ycc.yale.edu -----------------------------------------------------------------------------
wbonner@eecs.wsu.edu (Wim Bonner) (11/02/90)
In article <9011010808.AA05178@ucbvax.Berkeley.EDU> C08926RC@WUVMD.WUSTL.EDU (Rob Caton) writes: >I recently required a genuine IBM XT motherboard with 0k. The date on the >BIOS chip is 1986 and elsewhere on the board it says 256 - 640k. My question >is twofold: can this board be populated with 640k using 256x1 and 64x1 >chips, and if so, what are the proper dipswitch settings? You should be able to populate bank 0 and 1 with 256k chips, and do the next two rows with 64k chips. If you set the switches on the MB to indicate 256k the rom will automaticly count up to 640k. Wim. -- wbonner@yoda.eecs.wsu.edu 27313853@wsuvm1.csc.wsu.edu 27313853@Wsuvm1.BITNET 72561.3135@CompuServe.com