Hello,
have tracked down a weird CPU bug: if i do a soft reboot from within SETUP with CTRL-SETUP (a key combination from the the manual) the Z80 corrupts the 808x address space with stack data.
What i found out:
* BIOS begins an extensive memory test (BITTEST_AX) -
https://github.com/shattered/retro-...w100b/8086_DISASSEMBLY_23-022e5-00#L3931* problem gets visible at this location:
https://github.com/shattered/retro-...w100b/8086_DISASSEMBLY_23-022e5-00#L4175- BX is current address
- AL contains XOR result of correct and actual value
Z80 writes to $07f0/$07f1 (reflected at 808x offset $87f0/$87f1).
RESULT: ERROR 19 Main Board RAM (0-64K)
Why does the Z80 interfere with the memory test?
There is a reasonable suspicion the ZFLIP flag is set or handled wrongly. I just cant find where... P.S.: floppy test on the DIAG.DISK (from 'indiviual tests') now aborts with a 'Z80 response error'. Coincidence?
Any ideas? :-)
Screenshot of Z80 caught in the act:
https://dl.dropboxusercontent.com/u/37819653/BANNISTER/Z80_writes_to_8088_memory.jpg
