Opinion of Genesis sound capabilites and soud chips.

[Rex Dart]

The sound in the PCE/TG16 is a little before its time. It uses tiny wavetables to make sound. There are 32 five-bit samples for each channel in the sound processor. You can control the frequency and volume for effects. This is basically the same as later sound systems like the AWE64, just much smaller in scale. The tiny sample size limits fundamentally how low the frequency of the sound may be. It also limits how complex an instrument can be - it must repeat every 32 samples to avoid clicks.

 

You can do some nifty things with this - one of the neater is streaming the samples on the fly, allowing for 5-bit PCM with volume control. You can also set two channels to set volumes and stream two channels of samples for 10-bit PCM at a fixed volume. Games that stream PCM generally use the hblank int for sample rates at multiples of 15kHz, 7kHz being rather common.

 

The two biggest problems with Genesis audio are 1) they didn't tie the INT line from the YM2612 to the Z80, so the timers cannot interrupt the CPU, making them almost worthless; and 2) the lack of any ability to channel data to the DAC at a set rate - you have to use cycle counting on the Z80 (or HINTs on the 68000) to get a set rate on PCM. A lesser third problem is that Sega used a serially loaded register for the bank the Z80 uses to access the rom. A parallel loaded register would allow the Z80 to easily handle PCM at higher frequencies; the serial register takes about 100 clock cycles to load.

Alright, but is Air Zonk the best this system offers music-wise?

[Chilly Willy]

I'm not sure what the greatest is... and what was greatest to me someone else might call shit. Music is really very subjective. I personally like that old Amiga tracker music. Anything that sounds like that will be better in my opinion than anything else. Never got into FM music, although I do recognize great FM music when I hear it.

 

My favorite Genesis FM music is Ecco - The Tides of Time.

[Lynxpro]

The sound in the PCE/TG16 is a little before its time. It uses tiny wavetables to make sound. There are 32 five-bit samples for each channel in the sound processor. You can control the frequency and volume for effects. This is basically the same as later sound systems like the AWE64, just much smaller in scale. The tiny sample size limits fundamentally how low the frequency of the sound may be. It also limits how complex an instrument can be - it must repeat every 32 samples to avoid clicks.

 

You can do some nifty things with this - one of the neater is streaming the samples on the fly, allowing for 5-bit PCM with volume control. You can also set two channels to set volumes and stream two channels of samples for 10-bit PCM at a fixed volume. Games that stream PCM generally use the hblank int for sample rates at multiples of 15kHz, 7kHz being rather common.

 

The two biggest problems with Genesis audio are 1) they didn't tie the INT line from the YM2612 to the Z80, so the timers cannot interrupt the CPU, making them almost worthless; and 2) the lack of any ability to channel data to the DAC at a set rate - you have to use cycle counting on the Z80 (or HINTs on the 68000) to get a set rate on PCM. A lesser third problem is that Sega used a serially loaded register for the bank the Z80 uses to access the rom. A parallel loaded register would allow the Z80 to easily handle PCM at higher frequencies; the serial register takes about 100 clock cycles to load.

 

How does the 2612 compare to the 2151?

[Chilly Willy]

How does the 2612 compare to the 2151?

The YM2151 has two more channels (8 as opposed to 6), and needs an external DAC. The YM2612 uses an internal DAC, and you can switch FM channel 6 to PCM output.

[Lynxpro]

The YM2151 has two more channels (8 as opposed to 6), and needs an external DAC. The YM2612 uses an internal DAC, and you can switch FM channel 6 to PCM output.

 

Did Yamaha purposefully restrict the 2151 to their own projects outside of the arcade? I read Atari Coin/Games emails stating that was the case at least during the 1984-85 time frame.

[Chilly Willy]

Did Yamaha purposefully restrict the 2151 to their own projects outside of the arcade? I read Atari Coin/Games emails stating that was the case at least during the 1984-85 time frame.

No idea, but if they only restricted them in the middle 80's, it wouldn't have been an issue in the late 80's or the 90's.

[Lynxpro]

No idea, but if they only restricted them in the middle 80's, it wouldn't have been an issue in the late 80's or the 90's.

 

The [Atari Coin/Games] emails allude to it and seems to confirm a rumor that Yamaha wouldn't sell the YM2151 to Atari Corp for inclusion in the ST nor any other company they considered competitors in the home/professional marketplace. Yamaha was selling a MIDI music computer at the time that was going up against the ST. But seeing that the Genesis didn't even get the chip after 1988 either plays into this theory or Sega deemed it too expensive for its inclusion at the time...

[Chilly Willy]

The YM2612 was fine for the Genesis. They merely needed to do the following to have exponentially better audio:

 

Connect the YM2612 IRQ line to the Z80 so you can use the damn timers.

Make the rom access bank register parallel instead of serial.

 

That's it! There's more they could have done, but just those two changes would have put the Genesis audio on a whole other level.

[Lynxpro]

The YM2612 was fine for the Genesis. They merely needed to do the following to have exponentially better audio:

 

Connect the YM2612 IRQ line to the Z80 so you can use the damn timers.

Make the rom access bank register parallel instead of serial.

 

That's it! There's more they could have done, but just those two changes would have put the Genesis audio on a whole other level.

 

So the Z80 could directly control the audio like in their arcade units?

 

I'll never understand Japan's fetish for the Z80 whereas the American arcade companies went with the 6502 and the 6809 for the most part.

[Chilly Willy]

So the Z80 could directly control the audio like in their arcade units?

You could use either the 68000 or Z80... you were mainly supposed to use the Z80 for Genesis music. Some drivers use only the 68000, and a few use both the Z80 AND the 68000.

 

I'll never understand Japan's fetish for the Z80 whereas the American arcade companies went with the 6502 and the 6809 for the most part.

The Z80 was big for many companies... in the US, Tandy made a ton of Z80 based computers before finally switching to the 6809. The Z80 was huge in Europe as well. I think the main thing was companies trying to save every cent possible went with the 6502. The Z80 was powerful, but pricey, so you saw it in devices where the price didn't matter as much, like arcades and PCs. Home consoles liked the 6502 to keep the price low.

Edited November 9, 2014 by Chilly Willy