Panasonic FS-A1F and 128kb RAM upgrade

This happens because Testram tests all pages that are supposed to be present. Once it reaches 128KB+1, it writes 00h and there's no RAM chip present to read the value back. The FFh is then read from the databus pull-up resistors.

It's is correctly reporting what it found. But IMHO it should give a more detailed explanation for the problem, otherwise users without more intimate knowledge of the architecture will struggle to understand what is going on.

By the way, you also can test the 128 kB RAM upgrade with this BASIC listing from here See below.

On my machine it detects 128 kB without problem in DOS1 mode. Maybe this listing is useful to check how to detect the mapper in the correct way. First execute line 10 and then reload the BASIC listing and run it again (line 10 is now skipped).
If you don't do this you will end up in a Syntax error.

10 'poke &hf676,1:poke &hf677,&hc0:poke &hc000,0:new
20 DEFINT A-Z
30 PTR=&H8100:S=4
40 FOR I=4 TO 255
50 OUT &HFE,I
60 PTR=&H8100:FOR J=0 TO 127:POKE PTR,&H55:POKE PTR+1,&HAA:PTR=PTR+2:NEXT J
70 EF=0:PTR=&H8100:FOR J=0 TO 127
80 IF PEEK(PTR)<>&H55 OR PEEK(PTR+1)<>&HAA THEN PRINT "NG:";I:J=512:I=256:EF=1:GOTO 100
90 PTR=PTR+2
100 NEXT J
110 IF EF=0 THEN S=S+1:PRINT "OK:";I;S*16384/1024;"KB"
120 NEXT I
130 OUT &HFE,1
140 END

MSXMEM reports 512kB RAM instead of 128kB RAM:
https://m.blog.naver.com/zeta6262/80154575265

Did you try PA3 on these machines as well sdsnatcher73?

Funny thing is that if you use Carnivore2 in slot 1 and run TESTMAP, the error will be shown only at start and the 128kb mapper tests will be working fine from then on. I somehow feel that the modding instructions for A1F are not complete and something else needs to be bridged or cut on the motherboard. But my modest skills in electronics don't allow me to figure this out...