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MV-1C backup ram error

merrygoomba

merrygoomba

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My MV-1C suddenly boots with this error, FF36E330-904F-41EF-BBF0-C8A2126DCDBC.jpeg
Any idea what this means or what chip I need to replace, if any ? Thanks.
 
ack said:
It means the hardware test failed when testing backup ram. At address D00000 it wrote 0x0000 and when it read it back it got 0x0008. This is indicating the lower backup ram chip has an issue.

I recently documented all the ram locations for all MVS board (plus AES3-*), which you can find here for now.

https://github.com/jwestfall69/neogeo-diag-bios/blob/master/docs/ram.md#mvs-ram-locations
Click to expand...
Thanks for the link, excellent write up!, ordered some replacement RAM chips from mouser to see if it fixes it.
 
Received the RAM chips and installed them

3B8D7401-3FF3-43D0-8DC9-F076828FA54A.jpeg

and It seems to have worked ,I no longer get the error message, however I did receive this other error message the second time I powered the unit on

6306A541-5E35-4486-9265-ADB6994E6416.jpeg

after clearing the backup RAM I haven’t received any more error messages and it seems to all be fine now.Any ideas what that illegal instruction error message means ? Or what could have caused it?
 

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The address is within the bios and this is the code
Code: 
c13a54: 303c 0020                 move.w  #$20, D0
c13a58: 337c 7000 fffe            move.w  #$7000, (-$2,A1)
c13a5e: 3e3c 04ff                 move.w  #$4ff, D7
c13a62: 13c0 0030 0001            move.b  D0, $300001.l
c13a68: 3280                      move.w  D0, (A1)
c13a6a: 51cf fff6                 dbra    D7, $c13a62
This code is clearing the fix layer. Based on your D7 register it looks like it was able to do 18 of the 1280 loops, then crashed. You might verify your cart/cart slot is clean on the off chance the program rom thought it should have been enabled from a bad cart/slot connection.

Also, nice job on your ram swap. Looks really good.
 
ack said:
The address is within the bios and this is the code
Code: 
c13a54: 303c 0020                 move.w  #$20, D0
c13a58: 337c 7000 fffe            move.w  #$7000, (-$2,A1)
c13a5e: 3e3c 04ff                 move.w  #$4ff, D7
c13a62: 13c0 0030 0001            move.b  D0, $300001.l
c13a68: 3280                      move.w  D0, (A1)
c13a6a: 51cf fff6                 dbra    D7, $c13a62
This code is clearing the fix layer. Based on your D7 register it looks like it was able to do 18 of the 1280 loops, then crashed. You might verify your cart/cart slot is clean on the off chance the program rom thought it should have been enabled from a bad cart/slot connection.

Also, nice job on your ram swap. Looks really good.
Click to expand...
Thanks! I cleaned the slots and cart (NEO SD)prior to assembly, So far I haven’t been able to reproduce the error ,so It might just be the NEO SD was acting up ?( .
 
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