Hi Jim, On Mon, Apr 30, 2018 at 12:15:13AM -0500, Jim Brain wrote: >However, this is not true for the Ultimax video game configuration. In >that mode, the internal RAM ignores all memory accesses outside the >area $0000-$0FFF, unless they are performed by the VIC, and you can >write to external memory at $1000-$CFFF and $E000-$FFFF, if any, >without changing the contents of the internal RAM. > >Marko noted long ago that he was aware of a page the VIC could read >from, and there is this note on the list archives from 1999: > >http://cbm-hackers.2304266.n4.nabble.com/lt-Q-gt-C64-ULTIMAX-mode-td4059331.html I have nothing to add to that. Or maybe only a little detail: On the C128, you can write the EXROM and GAME lines on the MMU, and also switch to C64 mode (including UltiMax mode). If you make the VIC-IIe display the "external memory" (while nothing is connected to ROMH or ROML), then it will display the data read or written by the 8502. >Does anyone have more information? > >Also, on this portion of the archive: > >http://cbm-hackers.2304266.n4.nabble.com/Ultimax-questions-td4615195.html > >skoe notes that he was leery of just decoding the address lines because >of the state of $01. How would the state of $01 be of interest or >concern in Ultimax mode? In the PLA equations, both ROML and ROMH depend on HIRAM. ROML also depends on LORAM. Both LORAM and HIRAM are connected to the 6510 on-chip I/O port that is mapped to the data register at $01. Did you see this document from 2012/2013? http://www.zimmers.net/anonftp/pub/cbm/firmware/computers/c64/C64_PLA_Dissected.pdf MarkoReceived on 2018-04-30 12:00:02
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