On Thu, 12 Apr 101 g.baltissen@hccnet.nl wrote: > Hallo David, Nicolas, > > > > > I think, if you enable Ultimax mode, there is no RAM that can be > > written to. > > > This way you can use about every memory location above $1000 to map in > > your > > > own I/O. I just wonder if the SCPU is compatible with this mode. > > > > After _very_ careful interpretation of the PLA's reverse-engineered > > sourcecode, Bogax and I have decided that unless you're writing to the I/O > > page, you can't not write to ram. The only thing that throttles the WE > > line > > on the internal dram is the I/O outputs on the PLA > > The only thing I know, and even that could be wrong, is that Ultimax is a > "way" to replace the Kernal with an external one. The AR cart does it some way I cant particulary remember in mu just-woke-up state. ;) They do it this way so they can acess all the ram in the c64 and copy some of it to offboard ram(?) so that it can do its debugging/freezing work. Umax mode is a relic mode from the Ultimax game system based on the c-64. This machine had 2k of static ram and a simpler pla, as well as a slightly different vicII (no ram refresh), a single CIA for the joyports, and a cartridge port. The umax mode on the c64 emulates this memory map, plus tyhe 2k of extra ram on the game cart, if present. - This message was sent through the cbm-hackers mailing list. To unsubscribe: echo unsubscribe | mail cbm-hackers-request@dot.tml.hut.fi.
Archive generated by hypermail 2.1.1.