doppel, on Thu Jul 29, 2010 11:42 AM, said:
Hmmmm...well things seem to be slightly different on the PAL 7800. When I referred to "color clocks" I was referring to the 3.58 Mhz clock used both for the NTSC chroma sub-carrier and the TIA timing. I'm not at all clear on how the external PAL chroma clock affects the output versus NTSC.
Ok,I understand now,I have to say that I do not know for sure what a "color clock" is.I'm sorry my false! On the atari XL I think the GTIA clock is the color clock!?
I never actually said the CPU clock was fixed, in fact I don't recall mentioning the CPU clock cycles at all. But the figure of 114 (or is 113 or 113.5 now, these damn figures keep changing) should apply to the maximum speed of 1.79 MHz, naturally going down for any cycles spent accessing slow RAM or the TIA.
I think the same,with the CPU speed changing there will be always a different number of cycles.
It was you as I recall that mentioned there being 227 PAL color clocks per scanline (which, as I stated in the previous post, corresponds precisely to 454 MARIA clocks). How the external PAL clock of 4.43 MHz affects things, again, I have no clue, since I don't have any PAL hardware or any way of measuring any of this stuff.
I am sorry for that,I have used the term without knowing what it really means and I have just used it because others also use it
.On the PAL MARIA the PIN_3 has a different function from the NTSC MARIA because PAL needs this 4.433 "color clock"! This is only needed for the color coding and I think is not used for something else.
And as far as to why the hardware in a PAL 7800 would be clocked different from an NTSC 7800, I also have no idea. I'm gonna go ahead and stop right here, since I'm obviously not a hardware person...
I only have a PAL machine and maybe they have done things different with NTSC.I have also no definitive answer!
I have measured many other things like the DLL fetch transfers,DMA Startup/Shutdown,and I must say that the more I measure the more I am confused.It is really not easy stuff,the ones who design such things are real experts.I will take a rest for some days,maybe one day things will clean up...
<throws his hands up in frustration and walks away>
I am sorry I have not wanted that,I respect your opinion! My measurements were for PAL and yours for NTSC! Also my englisch is "machine" like and reads "hard" because I am no native speaker! But I do not want to blame anyone.I am sorry if it feels so.