Panasonic FS-A1F and 128kb RAM upgrade

@sdsnatcher73 my idea: maybe you can create a ramdisk (with command RAMDISK 4064) in DOS2 which will use all available RAM segments including the internal RAM. Put as many files from directory 1 on the ramdisk from an SD card so the complete ramdisk is nearly used. When completed, move those files back again to another directory (number 2) and compare both directories if the files inside it are the same using a hex editor. If those files are the same, DOS2 does handle the RAM segments in the correct way I guess. And I assume it will be okay as TESTMAP doesn't fail on DOS2 as it does the memory management.

But maybe it can be done easier

We already know DOS2 does something and actually as TESTMAP is not doing anything different it must be that the RAM now rolls over like on other machine (so on a 128kB machine segment 8 is actually segment 0). Has to be almost, but why???

This issue only shows under very specific software. For instance the Japanese MEMTEST that is used in the first upgrade works fine on the A1F with 64kB or 128kB. It seems mainly European software has issues with ROM segments in RAM mapper. Most probable is that no European MSX2 had similar setup and developers assumed it was the same on all machines with mappers (which is clearly not true).

Still most likely the 512kB and 4096kB upgrades ensure no ROM segments will be presented and European software will correctly identify the mapper size.

This page mentions that this NEC gate array is also used on the Toshiba FS-TM1 based on the Panasonic FS-A1. There is also a gate array on some Panasonic FS-A1 (version 3 of PCB), but apparently it's not a NEC chip.

Similar issues on these machines?

Thanks! Sadly, I could not find anything useful for our case there. But for the possible repairs this information may be quite useful.