Work Ram error mv1fzs

[kissedin]

Got this nice little board. With the stock bios it says work ram error write 5fa0 -> read ffa0.

I have tried to interpret this. But now i need help.

The first two letters differs should mean that it is the upper chip that is causing the problem. But ... Is that ram1 or ram2?

Furthermore. Ive calculated the adress to binary code
Write: 0101 1111 1010 0000
Read: 1111 1111 1010 0000

In my simple world that would be data line 16 and 14 that is causing problems. But there is no 16th data line on the chip (cxk58257am). Can someone please tell me how to interpret this right?

And finally. With diagnostic rom it passes the test but instead says: palette ram error 5555 -> 0055. Upper ram yes... But is that chip9 or 10?

 

[ack]

This should answer your questions

neogeo-diag-bios/docs/ram.md at master · jwestfall69/neogeo-diag-bios

Disassembly of smkdan's Neo Geo Diagnostics BIOS with added features - jwestfall69/neogeo-diag-bios

github.com

 

[kissedin]

Oh Yes! It really did help me! Ive read that page many times but now i saw the links to ram locations!

 

[kissedin]

And for the record. The Neo Geo uses two 8bit chips to create a 16 bit data package. So there is no dataline above 8.

 

[channelmaniac]

There are 2 ways to describe the data bus... D0-D15 or D1-D16. Mostly it's D0-D15 with D0-D7 being the lower byte and one of the backup RAMs and D8-D15 being the second, upper backup RAM.