Why would the 68000 just stop?
Posted: Mon Jan 04, 2016 11:02 pm
We've hit a weird problem with one of Montserrat's consoles over on the UMDK forum:
viewtopic.php?f=20&t=2239&start=195#p28406
This is a EURO PAL-i 1601-05 VA6 with a switchless mod by matt at dforce3000, failing to start Sonic 1. The SGDK-based UMDK menu program works fine, and the UMDK basic signal test passes, so it's not a dirty cart-slot problem. The same UMDK cart works on Montserrat's three(!) other consoles, one of which has the same switchless mod. Several other people have tested UMDK carts from the same manufacturing run, and none of them have shown similar problems. On this one particular console, it seems like the 68000 just stops fetching instructions, as if its clock has just stopped or the bus arbiter is permanently suppressing the 68000. There are some traces from UMDK's built-in logic analyzer in the post above, and there's an (older) analysis of a UMDK instruction trace in this post:
viewtopic.php?f=20&t=2239&start=180#p28339
Suggestions welcome!
viewtopic.php?f=20&t=2239&start=195#p28406
This is a EURO PAL-i 1601-05 VA6 with a switchless mod by matt at dforce3000, failing to start Sonic 1. The SGDK-based UMDK menu program works fine, and the UMDK basic signal test passes, so it's not a dirty cart-slot problem. The same UMDK cart works on Montserrat's three(!) other consoles, one of which has the same switchless mod. Several other people have tested UMDK carts from the same manufacturing run, and none of them have shown similar problems. On this one particular console, it seems like the 68000 just stops fetching instructions, as if its clock has just stopped or the bus arbiter is permanently suppressing the 68000. There are some traces from UMDK's built-in logic analyzer in the post above, and there's an (older) analysis of a UMDK instruction trace in this post:
viewtopic.php?f=20&t=2239&start=180#p28339
Suggestions welcome!