NES PAL timing vs NSTC timing and in general

NES PAL timing vs NSTC timing and in general
by Coldberg on 2011-12-24 (#87933)

i did some calculations it seems NTSC has a perfect 3:1 ratio of ppu cycles to cpu cycles but PAL has 3.20481928~~ is that correct ?
And how does that play out in synchronisation in making a cycle perfect emulator (like on nstc i'd run 1 cpu cycle and 3 ppu cycles but what about pal ? run 1 cpu cycle 3 ppu and then insert one ppu cycle for every 4 passes? sounds kind of a pain)
And how different ntsc/pal is actually ? cpu/apu/ppu what considerations should i take when coding say a nstc version then adapting it to pal?

Re: NES PAL timing vs NSTC timing and in general
by miker00lz on 2011-12-24 (#87936)

Coldberg wrote:

every 5 passes, add a PPU cycle. i don't see what is such a pain there. if the PPU tick modulo 5 is 0, do an extra tick......... it's no different than how you execute an extra CPU cycle on the NTSC version every third scanline.

NTSC CPU = master clock / 12
NTSC PPU = master clock / 4

PAL CPU = master clock / 16
PAL PPU = master clock / 5

http://wiki.nesdev.com/w/index.php/Clock_rate

there's a lot of info on the wiki. you should look at it.

by Coldberg on 2011-12-24 (#87937)

thanks
i tried looking at it but got a bit comfused

by johannesmutlu on 2011-12-28 (#88046)

no doubt that the timing between the pal and ntsc nes systems are different,wich explaines wich some pal,ntsc games,do,nt work on each other,even not with a clunky convertor,like the pirate version of superdonkeykong2(wich i run on the powerpak),it works on a ntsc nes,but not on a pal nes,all i get is a black screen, wich really pisses me off.
it,s so sad that some pal,ntsc games require crucial timing to work properly, aaarrrggg!!!