On Tue, May 08, 2012 at 05:23:10PM +0200, Gerrit Heitsch wrote: > On 05/08/2012 12:12 AM, Gábor Lénárt wrote: > > > >The other complicated solution would be disabling 6510 and allow uC to place > >data into C64's memory, so basically do some kind of DMA (from the view > >point of the C64 - I mean). Then I can have more tight timing, not needed > >to think about slower transfer by 6510 program, etc. > > If you do this, you will either have to disable the display or take > the bad lines into account. The latter meaning you have to watch AEC > to see whether you can have the bus or not. Yes, I found an old newsgroup thread about this, basically with the example of the Z80 based CP/M cartridge where the topic is the same: disabling the 6510 and "drive the bus" from externally (by the Z80 in that case). However it also made me think about one issue: as far as I remember there were some user feedback that CP/M cartridge had troubles on some C64 models, though I don't remember which ones and why. Btw, how much "used" the bus in C64 during normal conditions? I mean, is there any time left when neither 6510 and nor VIC-II uses it, so it's possible to use (slower) DMA with "running" CPU too. Sometimes that mode can be useful too, if speed is not the main issue. I guess it's not so much a realstic idea, as VIC-II even needs to steal cycles from the CPU from time to time (badlines, and I am not sure about sprites, but maybe then it needs extra cycles too). I am just curious here, I wouldn't do this anyway. Message was sent through the cbm-hackers mailing listReceived on 2012-05-08 16:00:32
Archive generated by hypermail 2.2.0.