On Thu, Feb 16, 2012 at 12:34:07AM +0100, Rob Clarke wrote: > Q1) As I understand it, I just need to fit the 16 missing drams and > decoupling caps? Yes. And, with some effort, the machines can also be extended to 1MB (960K usable). Not that there are any programs using this huge amount of memory:-) > 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? As far as I know the differences are only in the pinout. Some signals are on different pins, but the basic equations are the same. > Q3) The burn-in tests correctly identify whether the machine is a > high or low profile model. ANyone know how it programatically does > this? There are two input ports (PC6, PC7) on the 6525 that is connected to the keyboard. Their meaning is as follows PC6 PC7 ---------------------------------------- 0 0 CBM 6x0 PAL 1 0 CBM 610 NTSC 0 1 unused 1 1 CBM 7x0 > 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? I don't think so. > 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? Optocoupler has already been named. In the old days there have also been people who fed the signal by an 555 oscillator. Clock precision is low, but you don't have to create electronics that are connected to the high voltage mains line. Regards Uz -- Ullrich von Bassewitz uz@musoftware.de Message was sent through the cbm-hackers mailing listReceived on 2012-02-16 13:00:32
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