Following on from my success with the 610 two weeks ago, I have now got the 720 (mostly) working. Thanks again to all on CBM-H who've helped me out. Glorious green monochrome pic here, running the burn-in tests: http://inchocks.co.uk/commodore/B_Series/720Working.jpg The observant will notice that banks 3 & 4 are not populated. Although it's an immaculate 720 case, it's actually a 710 board. The board looks unused (there is not even any signs of scratches or oxidation on the IEEE edge connector) but as the case and monitor ar mint, I think I owe it to them to put another 128k on board. http://inchocks.co.uk/commodore/B_Series/720Board.jpg Q1) As I understand it, I just need to fit the 16 missing drams and decoupling caps? Q2) WRT to the differences in the PLA between the lo and high profile. I think I read somewhere that it was supposedly to be able to accomodate the coprocessor board. However, looking at the schematics, the PLA just routes RAS and CAS for the 4 memory banks, using all 8 outputs but just on different pins. Could someone explain where the differences are? Q3) The burn-in tests correctly identify whether the machine is a high or low profile model. ANyone know how it programatically does this? If you look at the pic below, I've had to jury rig the power, borrowing the PSU from my 610 to power the board while using the original PSU to power the monitor. As per my previous post, the PSU for the 720 is shot. Even adjusting the trimmer, it will only output 4.6v before cutting out. I'm happy to put a more modern PSU inside but this raises a couple more questions. http://inchocks.co.uk/commodore/B_Series/720PowerRig.jpg Q5) The case of the 720 PSU says it's rated for 80w but the back of the 720 says 120w, can someone else with a high profile machine clarify this? Does mine have the "wrong" PSU? Q6) I think modern ATX supplies have now dropped the -12V rail. From looking at the schematics this is only used for the RS232 port. As I'm not likely to use this any time soon, will I have any issues if I omit the -12V rail? Q7) The CBM-II PSU's all supply a 50/60hz signal from the PSU, which I think is just used for the TOD clock on the CIA. As I'm unlikely to find this on a modern PSU, is there a really simple way of generating this signal? Sorry for so many questions! Rob Message was sent through the cbm-hackers mailing listReceived on 2012-02-16 00:00:12
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