From: Nicolas Welte; address is valid for replies (Re:) only! (welte_spam_at_freenet.de)
Date: 2002-10-01 00:28:09
Hi, on Saturday I attended the Classic Computing meeting near Heilbronn, Germany and I had my PET 2001 with me. This was the first time I had this machine running a whole day, and it worked very well. It was also the first heavy duty test for the hardware I built to replace the old 6540 and 6550 chips, and all three boards worked very well: the system RAM/ROM replacement board, and the two little video RAM and ROM replacement boards. I also had a Userport video adaptor and Marko's C2N232 device with me. This was also the first time I used replacement I/O chips: Instead of the original 6520s I used two 68B21 that I bought just some weeks ago. I know we discussed it several times that the 6821 and the 6520 are pin and register compatible, so a 6821 should be a direct replacement, but nobody ever confirmed that this works. I didn't have any problems with them, the keyboard worked fine, the datasette ports and the IEEE port also worked fine. And instead of the original 6522 from 1978 I used a model from 1984, just to make sure noone damages it by abusing my PET. I heard some stories from Plus/4 users who "developed" a new kind of 8501 CPU replacement. They use a 8502 on an adaptor, and reprogram the KERNAL to be aware of the different I/O port bit mapping! I think the bit that is missing on the 8502 is connected to the serial port, so without the KERNAL patches no serial devices can be used. I also had the opportunity to copy the ROMs of a small screen PET 4016 onto my FlashROM expansion, and could then use this copy in my static PET 2001. Now I have a fully working set of BASIC 4.0 running in my 2001, which I was not able to to with the ROM images from Funet before. Now I wonder why this was so, because my new copy matches the one from Funet perfectly (revised BASIC 4.0 and non-CRTC editor for graphic keyboard). The only difference is an extra option ROM that I also copied, but I don't have an idea what it does. It might be related to the fact that this PET 4016 had a keyboard with japanese letters on it, but the character ROM is just the normal one. Nicolas Message was sent through the cbm-hackers mailing list
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