Hallo allemaal, I managed to make a sourcelisting of the 1541 Kernal by using my own generated one and the comments from Frank Kontros listing. Then I started to have a look how things work. And immediatly run into questions. At $EAC9 the ROM-test starts. It does this by adding all values. The thing I don't understand is $EAE2; "cmp $76". The result is compared with the contents of $76 which is the HB of the pointer to the ROM. As I understand it, the result of adding must be $E0 $C0 after the second run. Right? (I'm used to routines where the sum must be 0 (zero) at the end, that's why I'm confused a little bit) This means that each ROM must have a checksum byte somewhere. I found the one for the $E000/FFFF ROM at $FEE6. But I cannot find the one for the other ROM, anybody knows where to find it? Then a general remark: I think that my idea of using the 1541 kernal for my "Cheap IDE" project won't work out. Just have a look at the IRQ-routine. You'll find so many "typical real 1541" things that it won't be a matter of "converting it to IDE through a JMP" anymore. I think I'm better of writing my own Kernal and using the "good" parts of the original one. Any ideas, comment etc. is welcome. Another problem is to find a way to test the new Kernal. The logical thing is to use an EPROM emulator. But I don't have one :(. And burning/erasing EPROMs is not a good idea either I think. So started my second "Cheap IDE" project up: an IDE-HD for the C64. In less then an hour I hooked up an IDE-HD to my C64, the most work was drilling and filing a hole for the connector. Fired up the HD and C64 and the first results are promising: Keyboard works fine AFAIK and seems not to be disturb by the datalines of the HD. The advantage of this project is that it is just a matter of loading a PRG from floppy to test everything. I'll keep you informed. ___ / __|__ / / |_/ Groetjes, Ruud \ \__|_\ \___| http://Ruud.C64.org Message was sent through the cbm-hackers mailing list Message was sent through the cbm-hackers mailing list
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