On 11/15/2011 03:47 AM, Segher Boessenkool wrote: >>> Sorry for the mistake. I think that may have been an earlier design I >>> was remembering from Al Charpentier's notes about having to add a PLL >>> to keep them in sync. >> >> That was the VIC-II and all its derivates. In the end the decision to >> supply dot clock and color clock to the VIC-II independantly resulted >> in the need for the PLL and in the end gave us the little MOS 8701. >> Even though MOS reworked the VIC for the C128, the 8701 is still >> present there. > > The MAX machine used dual crystal oscillators (in discrete parts). The first C64 board had a layout that suggested that they had planned the same there: http://www.cbmhardware.de/c64/images/326298a.jpg I read somewhere that 2 crystals resulted in poor picture quality compared to using a PLL and only one crystal. Never understood why. > I don't think it would have been possible to make an 8701 in the > older 65xx NMOS process, 36MHz is too much. I'm surprised they were able to get 36MHz working with HMOS-II. > Are there die photos of the VIC-IIe somewhere? It would be interesting > to see what changed on there (what exactly changed functionally, anyway?) The VIC-IIe still uses the 8701, so the clock part didn't change. Otherwise it got a few I/O-Bits and the ability to switch the CPU clock between 1 and 2 MHz. More details can be found here: http://en.wikipedia.org/wiki/MOS_Technology_VIC-II#The_VIC-IIe Looks like there were some extra 'undocumented' features added as well Gerrit Message was sent through the cbm-hackers mailing listReceived on 2011-11-15 18:00:04
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