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Old 07 November 2019, 13:54   #5
AmigaHope
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Join Date: Sep 2006
Location: New Sandusky
Posts: 468
Quote:
Originally Posted by slaapliedje View Post
Whoa! I had no idea on that! Well crap, I wonder if that has been mucking with my PPC one then? How do you actually know you have a PAL 4000 or not, because I always thought that was kind of the reason Commodore put that on there, so they could just ship with a jumper set instead of a whole different board. Also, I thought the timing was all based on the crystal on the CPU card.
Edit: Holy crap, so all this time some of the random wonkiness was probably due to that. Freespace actually launched in OS4.1, but was gnarly for sure, under 3.9 it worked great (though I only got as far as loading up the docking bay after creating a pilot name). Gonna have to try some more things, would be wonderful if that fixed all my issues, I had no idea!
The board and chips themselves are exactly the same on PAL and NTSC A4000s (there is no chroma generator on it like on the A1200). The only difference between an NTSC and PAL A4000 is the crystal. The jumper is then set to tell the system that you have an NTSC or PAL crystal installed.

I made the same mistake as you initially, and jumpered my NTSC system to run in PAL by default, and it seemed to work fine at first. Then I noticed the longer I ran it the more messed up some things happened -- e.g. cryptographic connections like SSH and SSL would fail because timing checks were failing. Also timing in some games was off and would even cause some stuff like dropped frames.

Jumpering back to NTSC and just booting into PAL from early startup fixed those problems.

It all goes back to how NTSC crammed its colorburst into the existing 4.5Mhz black and white signal (not to mention slowed it by 1.001 to prevent interference, hence the 29.97fps) while PAL had more room in its 6Mhz bandwidth to fit the colorburst signal. It wound up such that it was pretty much impossible to make a single clock with high enough frequency to convert to the colorburst frequency of both systems with any easily-attainable division by an integer or simple fraction.
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