You don't want ISA memory expansion boards in a 386 except as a last resort for performance reasons

https://www.ardent-tool.com/Kingston/Files/Me … ory/KTM16at.PDF

jakethompson1 wrote on 2023-09-14, 22:52:

You don't want ISA memory expansion boards in a 386 except as a last resort for performance reasons

Compaq 386 doesn’t allow normal memory expansion options (no simms, no dipps)

Either a proprietary unobtainium memory card or isa .

The question is if you already have4mb/5mb on the planar is it worth having more RAM on a 386dx-16 ?

In dos the isa ram would be way up high so it wouldn’t affect most applications but in windows the kernel would be in the slow ram first.

386 needs a 32 bit data and adress bus, so the ISA slot is not sufficient for adressing the memory on the expansion cand.
All386 motherboards i know use proprietary slots for memory expansion.

What Compaq 386 do you own? there are different upgrade boards for the Deskpro /s (386SX) and the Deskpro/e (386DX).
Deskpro /N and Deskpro /M use PS/2 SIMMs so adding memory should not be a problem.
These were sold by Compaq as well as by Kingston, while there were additional manufacturers for the 1MB/4MB proprietary memory boards used on the mainboard as well es on the expansion card.

Thanks for the replies.

So it is a Deskpro 386s, which is the older-style 386 with no slots on the board for SIMMS. Looks like I would need to find a Kingston KTM-16AT or an unobtanium Compaq board that was made for this model.

But that being said with 1mb on the board and me only wanting to run DOS I suppose a memory expansion board isn't really necessary. My use-cases would be word processing, BBSing (MTCP and Procomm Plus), packet radio and games from that era. Shouldn't be a problem.

Cheers,
Doug

giantclam wrote on 2023-09-14, 22:58:

https://www.ardent-tool.com/Kingston/Files/Me … ory/KTM16at.PDF

🤣, okay I see it now. I was just looking at the KTM-AT silkscreened on the board. But now I see the sticker that identifies my board as a KTM-16AT/2. Thanks.

DougM wrote on 2023-09-15, 10:32:

Thanks for the replies. […]
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Thanks for the replies.

So it is a Deskpro 386s, which is the older-style 386 with no slots on the board for SIMMS. Looks like I would need to find a Kingston KTM-16AT or an unobtanium Compaq board that was made for this model.

But that being said with 1mb on the board and me only wanting to run DOS I suppose a memory expansion board isn't really necessary. My use-cases would be word processing, BBSing (MTCP and Procomm Plus), packet radio and games from that era. Shouldn't be a problem.

Cheers,
Doug

As an sx (16 bit data bus) with only 1mb just plop it in, it honestly can’t make things any slower and you loose out on a lot of software if you have less than 4mb.

DOS programs mostly won’t be hampered by “0ws” ISA memory because it’s the base memory speed that counts except for doom and later programs that won’t run well anyway.

Too bad the old 386 systems almost never supported cache

eisapc wrote on 2023-09-15, 07:03:

386 needs a 32 bit data and adress bus, so the ISA slot is not sufficient for adressing the memory on the expansion cand.
All386 motherboards i know use proprietary slots for memory

No, his system is a 386sx, considering ISA RAM is 0ws it may not significantly affect his performance.

And Yeah most of my 386 systems used simms or Ye olde dipps, even had a late Compaq 386sx that took 72pin simms

Well, after trying every combination of SW1 on the memory board and SW3 on the Compaq I've gotten nowhere. The memory count during post always stops at 1024. The board works fine in the 286 so I'm going to chalk it up to incompatibility. The only documentation available on the net is minuscule and addresses the KTM-16AT/4 and /6. My board is a /2 which stands for "give it up Doug" 🤣.

386s meant 386sx and you can find 16 bit memory expansion card easily, can take compaq style square daughterboard 1MB and 4MB modules. Make sure it is correct one. I see several on ebay except they are mostly 1MB base.

Cheers,

Yeah I just bought a Compaq 1mb board. Not ideal size but the price was right (less than shipping). It'll get me by for now. But man, when did shipping get so expensive! Ah well, first world problems...

DougM wrote on 2023-09-16, 18:20:

Yeah I just bought a Compaq 1mb board. Not ideal size but the price was right (less than shipping). It'll get me by for now. But man, when did shipping get so expensive! Ah well, first world problems...

How much ram did the 286 have?

A Compaq doesn’t just use more ram if you install it.
For starters the memory card needs its starting address just above your last onboard memory address making everything contiguous.
Even using the Compaq softpac disk to access the bios of your machine it may refuse to resize the memory size.

There is a hidden setting in the bios with the memory size, if the softpaq bios software won’t do it there are generic utilities that can sometimes modify the bios setting for base and extended ram.

Later Compaq machines would at least warn you on startup to hit an F key if it detected a change in your memory size. Early machines didn’t do so requiring a special bios boot up disk for your machine.