That's a really great work! When I evaluated the prototype received from commodore it was crashing All the time... someone from commodore said there was no hope to use this Board reliably. -----Message d'origine----- De : email@example.com [mailto:firstname.lastname@example.org] De la part de Michal Pleban Envoyé : samedi 21 janvier 2012 20:32 À : email@example.com Objet : Fixed the 8088 board in Commodore 610 Dear all, I would like to report a success in getting the 8088 board to work in Commodore 610 :-) As I mentioned in my posts a year ago, the primary reason that the board was not working is that a memory is getting corrupt during IPC calls from 8088 to 6509. The corruption pattern (every 128th byte) suggests that the DRAM signals (most probably CAS and RAS) are getting wrong and thus corrupting a whole DRAM page. The RAS and CAS signals are supplied to the DRAM chips directly from the PLA. During 8088 operation, the PLA drives these signals according to the ECAS and ERAS signals obtained from the 8088 board. These arrive via the P9 connector. It is easy to observe that on the high-profile motherboard, the PLA chip is located just near this connector, while on the low-profile motherboard it is far way from it. That means that these signals need to travel much longer way from 8088 board to PLA, and possibly suffer interference from other signal traces running on the motherboard. Thus, from time to time they get corrupted. The solution is simply to solder additional wires between these points; that is, from pin 40 of connector P9 to pin 26 of the PLA, and from pin 38 of connector P9 to pin 25 of the PLA. This gives the signals an alternate way of going through, reducing interference. Probably these wires should be well shielded to minimize problems; I just soldered two thin ones and it works about 80% of the time. When time permits, I will buy a good shielded wire. Here is a nice boot screen after the fix is applied ;-) http://a2.sphotos.ak.fbcdn.net/hphotos-ak-ash4/395995_10150482661642026_708927025_9004400_903114315_n.jpg Therefore we now know why the 8088 board does not work in stock 610 models. It's not a power issue, not a PLA issue, not a chip speed issue, not a signal termination issue. It's an issue of signal interference on the motherboard. With two pieces of wire, these problems can be easily overcome. Regards, Michau. Message was sent through the cbm-hackers mailing list Message was sent through the cbm-hackers mailing listReceived on 2012-01-21 22:00:05
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