Panasonic FS-A1F and 128kb RAM upgrade

Emulation is incomplete for A1F. There is something slightly different in the A1F compared to other MSX2 machines with mapper. On an unmodified A1F (which has a mapper of 64kB) the mentioned software (e.g. PA3) detects a larger mapper (probably 512kB but it is not reported). Other software is able to detect the correct size (e.g. RAMTEST and TESTMAP).

On openMSX the malfunctioning software also detects the correct size (so 64kB).

I have reported it to openMSX team but have not heard back from them.

There is not much we can do without further investigation. Please keep us updated ro!

Hello, a few days ago I received an fs-a1f from Japan, I was in the process of restoring it and I took the opportunity to put some sockets and expand the ram to 128k but before doing so I check with the msx diagnostics program it tells me I have 512k, can someone tell me why?

So, can someone please figure out which detection method is used in these programs?

This error is caused by a mismatch between the number of active output bits (*1) in the memory mapper registers and the actual number of existing pages. People who are building their omegaMSX are getting similar errors when they mess up with the memory configuration jumpers.

TestRAM is very strict on its testing. Too sad it's not very clear when it comes to explain Memory Mapper register size mismatch. I wonder if the source code is available somewhere.

Under normal conditions, this mismatch should cause no problem. But a difference between the number of active mapper register bits and the number of existing RAM pages is known to cause poorly written software to fail.

It's similar to the problem that some software have with split-RAM configuration.

For developers wanting to avoid this bug: The MSX Acid3Test covers this situation.