2MB populated "8 MEG AT RAM" board

[kishy]

I pulled this, working, from my PS/2 30 286 years ago (in 2011, to be exact, when it was replaced by a board that takes SIMMs).

It has 2MB installed, of a max of 8MB. View photos here: https://imgur.com/a/cx7Js

I have not used it again yet, and suspect I never will, so it's available for anyone who wants it. $30 plus shipping, payment by PayPal, shipping via Canada Post, will ship anywhere.

Once someone voices interest in this, I will pop it back in the PS/2 to make sure the POST memory count comes out as expected.

 

[Druid6900]

I have one identical to this a well.

Only difference is the printing on the LSI is rotated +90 degrees.

I tried this in a 1 Meg 286 but it didn't see it. Is this extended or expanded memory?

 

[kishy]

I have one identical to this a well.

Only difference is the printing on the LSI is rotated +90 degrees.

I tried this in a 1 Meg 286 but it didn't see it. Is this extended or expanded memory?

Colour me a noob for it, but I have never understood the difference. All I know is that the PS/2 POST memory check counted it together with the memory on the motherboard.

If there's a specific process (e.g. does the MS-DOS mem command tell us this?) that I can do to find out for you, please share, and I'll get the info.

 

[GiGaBiTe]

Colour me a noob for it, but I have never understood the difference.

The original 8086/8088 could only address 1 megabyte of RAM owing to its 20 bit address bus. When the 286 came around, it had a 24 bit address bus and could address up to 16 MB. the 386DX had a 32 bit address bus and could address up to 4 GB.

Extended memory (XMS) refers to the entire memory area beyond the original 1 megabyte limit in the 8086/8088 (1 MB - 4 GB.) In order to access the memory map beyond 1 MB, the processor had to be switched into protected mode, which had a couple of problems. DOS doesn't support protected mode natively and requires something like DPMS runtimes or application support and additionally the 286 doesn't support going in and out of protected mode without rebooting the computer.

Expanded memory (EMS) on the other hand is a name for a bunch of different incompatible DOS memory management programs, EMM386 being one example. The memory manager would create a window in conventional memory (usually 16-64 KB) which mapped to pages in the upper extended memory area, which were then bankswitched in and out of the window in conventional memory.

 

[kishy]

Thank you, that's a very clear and simple way to put it. I was aware there was a limit (I thought it was 640K, actually...) and that memory above it was handled "differently", but I thought it was more seamless than it sounds now.

Does the fact that the POST memory count can see the RAM on this card indicate anything regarding how this card works? e.g. would you expect that the BIOS normally not be able to see expanded memory, therefore making this certainly extended memory?

 

[GiGaBiTe]

Thank you, that's a very clear and simple way to put it. I was aware there was a limit (I thought it was 640K, actually...)

640k is the amount available to DOS, the next 384k is used for various memory mapped peripherals like the system BIOS, CGA/EGA/MDA/VGA BIOS, ports, etc. EMS usually uses a chunk of memory in the upper 384k to avoid consuming the 640k available for DOS, but some conventional memory is lost because it's loaded as a TSR. FreeDOS has a larger chunk of conventional memory available, something like 700-740k because it reclaims some of that reserved space for option ROMs. This is nice for conventional memory hungry applications (Duke Nukem II comes to mind) which would otherwise need special autoexec.bat and config.sys configurations to free up memory.

Does the fact that the POST memory count can see the RAM on this card indicate anything regarding how this card works? e.g. would you expect that the BIOS normally not be able to see expanded memory, therefore making this certainly extended memory?

If the BIOS can see the memory present on this card, I would expect it to be extended memory (XMS.) Some memory boards were proprietary and required drivers in order to work.