1MB memory on IBM 5160?

[Springbok]

Stupid question I am sure, but is it possible to get a 5160 with 640KB memory to recognize a 384KB memory expansion card?

 

[cruising]

Stupid question I am sure, but is it possible to get a 5160 with 640KB memory to recognize a 384KB memory expansion card?

If im not got this wrong, 640K is maximum if you aint do any modifications. Someone else will have a better answer for this.

 

[reenigne]

Yes, it's possible. The problem is that some of the address space in the range A0000-FFFFF is needed for the BIOS ROM, video RAM (and ROM, in the case of EGA/VGA), fixed disk controller ROM, other add-in ROM and devices, and EMS page frame. So you won't be able to use all of that 384kB unless at least some of it is mapped as EMS. Also, you won't be able to all (or possibly any) of it as normal conventional memory - some software won't recognize conventional memory above A0000 even if you tell DOS and the BIOS that it is there (and that address space is required for EGA/VGA video RAM anyway). You can load big chunks of (later versions of) DOS and some drivers in UMBs though to maximize the amount of conventional RAM.

 

[sergey]

Stupid question I am sure, but is it possible to get a 5160 with 640KB memory to recognize a 384KB memory expansion card?

I am assuming that you're talking about a memory card that is intended to expand the memory of an XT or PC with 256 KiB on-board memory to 640 KiB (256+384 = 640). Something like this card. In this case the answer is NO - you cannot use such card, it will map the memory in 40000h-9FFFFh range, overlapping with the on-board memory.

Now there are some other ways to expand the memory:

• Using a UMB memory card. This card is not difficult to build (see this thread), and it basically maps into otherwise unused memory, normally in 0C0000h-0EFFFFh range. So you can have a maximum of 192 KiB here. UMB is only supported in MS-DOS 5.0+. DOS can use UMB to load some of its (DOS) parts and device drivers.
• If you don't have VGA/EGA, it might be possible to use 0A0000h-0AFFFFh range as well, giving you additional 64 KiB of RAM. The problem here is that BIOS data memory (413h) needs to be updated with the correct memory size before loading DOS. Which probably would require either hacking the system BIOS, or crafting a BIOS extension ROM that will do so.
• Using a LIM EMS memory card. This only helps if you have a software that supports EMS memory. It also might be possible to use EMS as UMB (but it is a bit wasteful).

 

[Stone]

I have several 256K cards by RYBS that can be set to start at 640K (or anywhere below that) and come with software to utilize the upper RAM for RAMdisks, printspoolers and TSRs, etc.

 

[modem7]

A diagram for the IBM 5160 is [here].