From: Gideon Zweijtzer (gideonz_at_dds.nl)
Date: 2003-07-06 19:18:50
Spiro, > Mario wrote that there are colored squares *instead of* > sprites when inserting a cartridge, so I assume that there > are indeed sprites, but they have a wrong content. That was > the reason for my advice. My appologies, I missed that part of his message. It is difficult to say anything when it comes to using a cartridge, because the code used in the cartridge is usually not known. I read Mario's second messgage, and it seems that the wrong data is being read by the VIC-II. The colors are okay, so wrong writes to the VIC-II are not likely, as the border color or other colors are likely to be overwritten. This could indeed be the CIA#2 for the A14/A15 lines, but I have also had a C-64 before where logic IC's were broken (the ones that you'd never expect to get flaky!). The A14/A15 lines go through multiplexing logic before it arrives at the VIC-II. I think that with an oscilloscope the bad guy can be found easily. Antoher method is, when you can still type (blindly) is to type a small program to copy the character ROM to RAM, and switch the VIC-II to retrieve the characters from there. (The addresspath from the VIC-II to the ROM is different from the path used by the CPU to the ROM!). You could try this in different banks. With some logic reasoning, you'll find out where it goes wrong. This is how I found out once that the 74LS373 latch was broken. Gideon Message was sent through the cbm-hackers mailing list
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