Hi! On Mon, Dec 20, 2010 at 07:36:50PM +0100, Groepaz wrote: > - would b500 line machines use the same cpu clock as c64s ? i assume yes here, > correct? Yes. It has the same graphics chip with identical timining requirements to generate video output. > - for 6x0/7x0 machines, is the exact cpu clock really 2Mhz? a comment in the > vice source suggests it is, but actually a lower clock is used to work around > some ieee timing problem. again a bit odd :) Yes, it's 2MHz, derived from a 18MHz crystal source. The master clock ("dot clock") is divided by 9 using an 8 bit shift register. It does actually generate several skewed 2MHz signals. This allows a very precise timing. Not sure about ieee timing problems. As far as I know there are no provisions in the "real machine" to lower the clock. > - for 6x0/7x0 machines, is again the only difference regarding 50/60Hz > machines the roms? Not even this. The kernal is identical. The video initialization depends on two input signals on one of the 6525chips. One switches between PAL and NTSC (and also between 50 and 60 Hz), the other between internal (CBM 7x0) and external (CBM 6x0) monitor. Most of this is from memory, please correct me if I'm wrong. Regards Uz -- Ullrich von Bassewitz uz@musoftware.de Message was sent through the cbm-hackers mailing listReceived on 2010-12-20 20:00:05
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