[Bug 1667] Regression - No Video in RealPlayer 8

Wine Bugs wine-bugs at winehq.com
Wed Dec 10 04:31:27 CST 2003


http://bugs.winehq.com/show_bug.cgi?id=1667





------- Additional Comments From Andrew.Talbot at talbotville.com  2003-10-12 04:31 -------
Mike,

OK, here are some results that spoil the party!  Because I didn't want to overdo 
the detail earlier, I deliberately omitted to mention that the Programmable 
Interval Timer chip is fed from a crystal which oscillates at 3.579545 MHz, 
(which just happens to be the chroma frequency for NTSC-N).  Divide this by 
three and you get 1.193182 MHz.  Now, it was rumoured that some PCs use the 3x 
clock straight, but I was sceptical - big mistake!

I have just tested five PCs from three different UK manufacturers, ranging from 
a P2/400MHz to a P4/2.4GHz, most with Windows XP Professional, one with XP Home 
Edition and, guess what, yep, they *all* show a QPF of 3579545!

I think it is true to say that Microsoft do not state what frequency one is 
going to get when one uses the High-Performance Counter.  So, I am rapidly being 
drawn to the conclusion that we should forget about the RDTSC instruction 
completely and just concentrate on getting whatever the PIT chip provides.  I 
gather this 82C54 chip takes the 3.58-MHz signal (as used by XP) and produces a 
divided-by-three output (1.19 MHz, as used by Win98) and a 
divided-by-a-further-65536 (18.2 Hz) output.

-- Andy.


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