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Chris
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Confusing Sound Hardware Questions
 Posted: Wed Apr 05, 2000 5:46 am
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What is the major difference between the Pokey and the SN9xxxxx chips? They both have 3 channel PSG sound, they both have 1 noise channel, I don't get it. Is one more popular than the other?
Also, I did some investigation on the bizzare Yamaha chips again and this time I found out that the YM2203 is some type of merged chip. Some of the experts might agree that the YM2151 came out before all these other chips and that had 8 channels preset
instruments. Example of the YM2203:
YM2203
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----PSG--- Channel A
| |---- Channel B - All make square wave noises
| |---- Channel C /
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-----FM--- Channel 1
|---- Channel 2 |
|---- Channel 3 - All make synthesized melodies
|---- Channel 4 |
|---- Channel 5 /
If my investigation was correct, and the Yamaha 2203 internally has support for both PSG and FM sound, why doesn't the YM2612 have PSG sound support like this? What's even more strange is that the YM2413 came out after the YM2203, but it only has 6 channels of sound and they aren't even programmable!! And what's the story with the YM2610? The YM2610 is kinda mapped out like this:
YM2610
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----FM---- Channel 1
| |---- Channel 2 |
|---- Channel 3 - All make synthesized melodies
|---- Channel 4 |
| |---- Channel 5 |
| |---- Channel 6 /
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----PCMA-- Channel 1
| |---- Channel 2 |
| |---- Channel 3 - All simultaneously playback samples
| |---- Channel 4 | at certain set frequencies
| |---- Channel 5 |
| |---- Channel 6 /
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----PCMB-- Channel 1 - Plays back sample at certain
frequency.
If they took the time to make the YM2610 into such a powerhouse chip, why did they even bother to make a YM2612 in the first place? The YM2612 doesn't even have a PCMA or PCMB. It has a DAC but I think that's only Genesis specific and it's external.
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- Joined: 25 Oct 1999
- Posts: 2029
- Location: Monterey, California
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Posted: Wed Apr 05, 2000 5:31 pm
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Quote > What is the major difference between the Pokey and the SN9xxxxx chips? They both have 3 channel PSG sound, they both have 1 noise channel, I don't get it. Is one more popular than the other?
Er, if the Pokey that's used in the Atari bits is the same Pokey you're talking about, they're quite different.
The Pokey chip has two sound channels, either of which can be set to various types of tone generators (square, sine, triangle, sawtooth, white noise... I -THINK-. it's been a while).
The SMS's chip has a greater tonal range than the pokey (only 255 steps, which had trouble approximating certain musical pitches). Both offer 16 volume levels.
The Atari 8 bits had two pokeys, for a choice of four channels... little known trivia fact: Each pokey output to a seperate channel, so the 8-bits could do stereo sound, although the default RF modulator combined them into one.
I don't have specific information about the yamaha chips, but keep in mind that's it's not at all uncommon for a manufacturer to release a less powerful/functional version of an existing product model, if the market exists for a less expensive chip with fewer features. Example: Intel's Celeron, which came out after the Pentium II.
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