Ethan Dicks wrote: > ASSY 326298 > REVB (C) 1982 > COMMODORE 64 The ASSY number is the key to identify each board. The C64 service manual (also online on funet, I think) lists this number as 'original board'. There also is a version A, B, B-2, B-3 and E board. The respective numbers are 250407, 250425, 250441, 250446, 250469. The E board exists in two different revisions, one with a discrete color RAM chip (rev 3 and rev 4), the other without one (rev B). The schematic of the original board suggests that there is a PAL/NTSC jumper, it should be a jumper wire like in the version A board that can be put either on location E2 or E3. The board layout shows an empty space near U29 in the video cage, maybe this is where the jumpers are. > Right. The ROMs page on funet mentions that the RS-232 constants assume > a 1.0Mhz CPU (my guess is that they forgot to update the numbers from > the V(I)C-20. I used to use this with a VIC-modem, so at least at 300 > baud, it's close enough. The early 6567 chips also had a different timing that looks like it was made for exactly 1MHz system clock. This is also the clock frequency of the Ultimax computer which uses a 6566 VIC-II chip. Maybe they made a last minute change in the C64 for unknown reasons, and the video chip and the ROM were left configured for 1MHz. And I think the VIC-20 runs at significantly higher clock speed, perhaps 1.2 MHz. I forgot ;-) It's a pity that you don't have your original C64 anymore. There's always the search for early chips to explore funny bugs. I think Andreas Boose wanted to know once if the reset bit, that is disabled in all known VIC-II chips is perhaps active in very early versions. Perhaps you could try it on your machine? Nicolas - This message was sent through the cbm-hackers mailing list. To unsubscribe: echo unsubscribe | mail cbm-hackers-request@dot.tcm.hut.fi.
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