Old MMU inserted RAM upgrade question

[coonsgm]

I have a 1040STF with a RAM upgrade board that uses the shifter and MMU sockets (similar to the Marpet and Exxos style 4mb upgrades). This one is populated with 1.5mb of RAM adding to the 1mb on the board.

The computer wouldn't run to begin with, but I've gotten it running and have run a number of tests on it. One thing is confusing me.

When checking for total RAM with Sysinfo and any other program in TOS I get 2.5mb. YAART results...0 errors after 5 passes.

However, when using the Diagnostic cartridge and testing there, I only show and test 1mb.

Is this expected? Anyone see something like this before?

[exxos]

Not totally sure, but think 2.5MB was a bit of a hack and wasn't really a official ram amount.. I guess you could try the STE cart, it will moan a lot, but might have a better ram test :shrug:

[coonsgm]

Hah, I wish I still had my SideCart. I only have the ST / STF / Mega diag cart :(

[frank.lukas]

Sysinfo does not test the RAM properly and simply assumes that the Atari can have two RAM banks with 512k or 2048k each. But there are also RAM extensions for a total of 3MB ...