> It depends much on how much extra stuff you want to have in your > design. I'm mostly thinking about 5V/3.3V issues. 5V devices are > hard to come by these days. The original devices do not output 5V either (they use NMOS push/pull totems for output, so the high output voltage is about 5V minus the enhancement mode threshold voltage). Have a look at http://segher.ircgeeks.net/c64/plots/vic.html for some nice plots (thanks Gerrit!) As you can see, the outputs from the 6569 are about 3.5V, and those of the 8565 are about 3.4V. The outputs from the CPU (6502/8500) are a bit higher, 4.0V resp. 4.5V here. The outputs from the 82S100 are only about 3.6V (and they dip a bit); the 82S100 is a bipolar device, not MOS. Finally, the outputs from the big CMOS chip on the newer C64s is 4.9V or so. And, of course, you need to get the timing right as well (there is a significant delay *everywhere*, this is old stuff). 3.3V might actually work better than 5.0V... Segher Message was sent through the cbm-hackers mailing listReceived on 2012-09-03 05:00:04
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