* On Sat, Apr 25, 2015 at 02:54:35PM +0300 Marko Mäkelä wrote: > Yes. Actually, I made a mistake in my previous post by claiming that > the PAL/NTSC detection does not affect anything. Now that I think > more carefully, the CIA timer interrupts for RS-232, tape, and for > the regular $ea31 interrupt must be at a fixed rate, so they must be > adapted for the different 6510 clock frequency in the C64 > (17734472/18 Hz on PAL and 14318181/14 Hz on NTSC). Correct, except for the (prototypical?) -01 ROM, which assumes a fixed rate of 1 MHz. > The timer interrupt should be 60Hz. It is not 50Hz in PAL models, > and I guess it is not synchronized with the 6567 screen updates in > NTSC models either. Correct again, it is not synchronized in any way. > AFAIU, the C64 KERNAL is very close to the VIC-20 one, and very > little software depends on the ToD clock. GEOS is one example. It is extremely close to the VIC-20 one. I was very surprised how similar they are when I created the source that compiles either ROM set (BASIC + KERNAL). I never expected it this way. Regards, Spiro. -- Spiro R. Trikaliotis http://www.trikaliotis.net/ Message was sent through the cbm-hackers mailing listReceived on 2015-04-26 19:00:06
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