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Old 02-19-2006, 12:30 AM   #6
Disch
Senior Member
 
Join Date: Apr 2001
Posts: 4,387
Default Re: nes emulator with cpu core frequency settings?

> Hrm, there was an emulator out there that had pitch for the
> [collective] dsp output, IE you could half the playback
> speed of the music without affecting the speed of gameplay.
> Wondering if maybe some sort of compensation feature might
> be appropriate.

Well you could tweak it to work that way. I just didn't bother for this test.

The reason the pitch changes is because the NES's pAPU is actually part of the CPU. So sound hardware is clocked at the same rate as the CPU. Increasing CPU speed means increasing how fast the hardware gets clocked (increasing the frequency of the played tone). Doubling the clock rate effectively makes everything an octave higher in pitch.

This is the reason why PAL plays music at a slightly lower frequency than NTSC (PAL CPU clock speed is a bit slower).
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