Last weekend, I ported the custom transfer routines of my cassette-RS232 adapter to my CBM 720 (also known as High Profile B-256). Everything else worked nicely, but I can't relink or run BASIC programs. I disassembled the BASIC ROMs (901241-03 and 901240-03) in order to find the following addresses: clr = $8a27 linkprg = $869c stxpt = $b41a newstt = $8752 In the Commodore 64, the corresponding addresses are: clr = $a659 linkprg = $a533 stxpt = $a68e newstt = $a7ae What I found is probably not fully equivalent to the C64 routines, because once I've loaded a BASIC program to $010003 using this version of prlink and try to LIST it, the listing continues with rubbish. Using the machine language monitor (commands SYS60950, V01 and M0003), I found out that the last three zero bytes of the program were overwritten (the middle byte was nonzero). I verified that the culprit can't be the linkprg call, but I couldn't figure out which zero page variables in bank 15 could affect this. Can anyone tell me how to solve this problem, or to perform a RUN command in machine language on these computers? For the P500 (which I assume is the same as PET II series model CBM 500), I have quite little information. Judging from the SID note table in the user's guide (which should be scanned, I know, but I lack the time and the equipment) and from the schematic diagram, the B-128 and B-256 run at 2 MHz, but I'm not sure about the P500. Is it 1.022727 MHz like other NTSC computers, or 985248 Hz like the PAL C64, or something else? Also, which firmware does this machine run? The firmware hasn't been archived on FUNET (yet; hint to the P500 owners on this list). Speaking of the firmware, my 720 has otherwise the same KERNAL as "kernal.901244-03.swedish.bin" on FUNET, but the $aa padding bytes at $edf8-$edff have been changed to 62 f2 a5 6d 5e 80 85 e9. Does anyone know what this patch could be? I should write up the Commodore part numbers on the chips and to read the contents of the character ROM at some other point. Please help me create a _portable_ data transfer solution for _all_ CBM 8-bit computers. (Any PET BASIC 1.0 users out there?) Marko Message was sent through the cbm-hackers mailing list
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