On 12/11/2011 10:08 PM, Spiro Trikaliotis wrote: > Hello, > > JFTR: > > * On Sun, Dec 11, 2011 at 09:04:07PM +0100 Gerrit Heitsch wrote: >> On 12/11/2011 08:28 PM, Spiro Trikaliotis wrote: >>> Hello Gerrit, >>> >>> * On Sat, Dec 10, 2011 at 09:14:03PM +0100 Gerrit Heitsch wrote: >>>> On 12/10/2011 08:51 PM, Segher Boessenkool wrote: >>> >>>> I don't plan on using the 6569R1 regularly. But it's nice to have a >>>> really old C64 (includes real PLA and -02 Kernal ROM) handy when >>>> checking software compatibility. The RAM test I use crashes on the >>>> -02 ROM, plug in a -03 ROM and it works. >>> >>> Why does it crash on a -02 ROM? I mean, the differences between -02 and >>> -03 are very small. >> >> I asked myself the same thing but didn't see a reason to investigate >> in detail yet. The problem was reproducable though. > > Looking into the code, it is obvious: The code writes directly into Video > RAM ($0400-$07FF), but never writes the color RAM ($D800-$DBFF). As the > -02 ROM initializes the Color RAM to background color, you do not see > the output. Ah, OK, that explains things. Still means the program is not usable with a -02 Kernel ROM unless one thinks about the workaround before running it. > BTW: The test is extremely simply and would not find many erroneous RAM > chips, anyway. So far the only defective RAM I had in these old systems was either stuck bits (very often the MT4264) or a complete core meltdown (system doesn't start up at all, defective chip gets very hot very fast) So it's better than nothing. Always open for suggestions for a better test program though. Gerrit Message was sent through the cbm-hackers mailing listReceived on 2011-12-12 17:00:25
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