Would probably help if you posted pics of the cards in question, or at least gave what info you have (any text on the PCB or labels on chips)

rehiv wrote on 2022-06-02, 05:13:

Ran across these three 8-bit RAM cards, none of them showed up as memory during the memory count during boot up which makes me think they are EMS/LIM cards?

Pictures would help! I'm assuming here that you have ordinary RAM expansion cards...

On XT class machines you need to set some switches on the motherboard to tell it how much RAM exists, and also need to set some switches/jumpers on the memory board to assign it a starting memory address and tell it how many 64K banks are populated. Most of these cards have 6 banks (384K) and are meant to bring a 256K PC/XT motherboard up to the maximum 640K, so they'll usually have 6 columns of memory sockets with 9 sockets (8 bits plus parity) per column.

All AT class machines (286 and up) will have at least 640K on the motherboard, so ordinary 8-bit RAM expansion cards are pretty much useless in a 16-bit ISA system. I don't think it's even possible to test the board's memory using a typical 16-bit ISA motherboard.

^That's mostly right, yes.
Some modern XT compatibles may have a CMOS Setup, though. And an RTC, maybe.
- I'm thinking of PC1512/1640 and of certain Atari/Commodore PCs.

That also includes old PC emulators (hardware solutions).
However, they aren't exactly clones of the PC/XT motherboard from IBM.

640KB on ATs.. Yes and no. Yes, 640KB were the norm.
But some of their CMOS Utilities allowed dividing 1MB into 512+512 and/or 640+384 (base memory+extended memory or shadow RAM).
So it's theoretically possible to set it to 512KB, and use an UMB card to fill in 128KB into 512-640KB, and the rest into free areas of UMA. 🙂
That way, more motherboard RAM is available as Extended Memory (can be used by XMS/Himem.sys).

Edit: Edited.

Jo22 wrote on 2022-06-02, 19:54:

640KB on ATs.. Yes and no. Yes, 640KB were the norm.
But some of their CMOS Utilities allowed dividing 1MB into 512+512 and/or 640+384 (base memory+extended memory or shadow RAM).
So it's theoretically possible to set it to 512KB, and use an UMB card to fill in 128KB into 512-640KB, and the rest into free areas of UMA. 🙂

Exciting! I need to find a 286 and also an EMS/LIM card to add to my collection. So far I've just been slumming it in 8088 land with 640K. That ought to be enough for anyone, right?!

Jo22 wrote on 2022-06-02, 19:54:

640KB on ATs.. Yes and no. Yes, 640KB were the norm.
But some of their CMOS Utilities allowed dividing 1MB into 512+512 and/or 640+384 (base memory+extended memory or shadow RAM).

On the original IBM AT, the mainboard was completely filled with RAM chips at 512 + 0.

The first generation of IBM memory expansion cards for the AT were 128K conventional memory to go to 640 + X and 512K of extended memory (multiple cards allowed for multiples of 512KB).

The second generation of IBM memory expansion cards for the AT included a card that combined the 128K conventional card anf the 512K extended memory card onto one card (by using higher density chips for the extended memory), and a card that provided 2MB of extended memory (and no conventional memory). Again, multiple 2MB cards were possible.

Only with the advent of the third generation of IBM memory options, based on SIMMs instead of single chips, an original IBM option was available to "split" a bank between extended memory and conventional memory to obtain something like 384KB extended memory.

IBM switched over to their proprietary MCA-based PS/2 line after the AT, so there is no original IBM AT-like mainboard with a 640+384 split. On the other hand, you are right that many later AT-compatible chipsets supported 640+384 out of the box, and the more advanced AT clones (most prominently the "New Enhanced AT" (NEAT) chipset by C&T) even supported changing memory layout in the setup utility.