PSG upgrade with an Microchip AY8930

Door gdx

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03-06-2021, 11:11

Has anyone tried to replace the PSG on their MSX with a enhanced PSG AY8930?
I think there is just to replace the chip to upgrade the MSX.

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Van JohnHassink

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03-06-2021, 11:45

Nowadays, I guess Darky is the most elegant and easy solution? Smile

Van gdx

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03-06-2021, 11:52

Finally, the AY8930 is not 100% compatible. The last 3 registers are different.

Van ToriHino

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03-06-2021, 12:30

JohnHassink wrote:

Nowadays, I guess Darky is the most elegant and easy solution? Smile

Yes, in fact Darky supports even two AY8930 chips (and an effects processor).

Van Grauw

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03-06-2021, 12:42

gdx wrote:

Finally, the AY8930 is not 100% compatible. The last 3 registers are different.

Are you looking at the correct table in the application manual? In compatibility (default) mode it should be fully compatible with AY-3-8910. In VGMPlay I don’t really treat it different from normal PSGs.

I think the biggest hurdle to upgrading the PSG in MSX computers (with either AY8930 or YM2203) is that not that many machines have a discrete PSG, most have it integrated in the MSX-ENGINE.

Van gdx

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03-06-2021, 13:03

I must have taken the wrong page.

YM2149 registers:

AY8930 default registers:

Van mars2000you

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03-06-2021, 13:03

What is 'Mode select" ? I think grauw is referring to that when talking about default mode.

Van gdx

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03-06-2021, 13:25

It's to access to the enhanced modes.

I think 1010 and 1011 are for enhanced modes and other values are for the compatible mode. Right?

Van mars2000you

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03-06-2021, 13:14

It's explained here : http://www.vgmpf.com/Wiki/index.php?title=AY8930/P

"In Compatible mode, the AY8930/P had the same 3 channels with the same enveloping, volume, and clock speed as the AY-3-8910. In Expanded mode, the chip give a unique envelope to each channel, variable duty-cycles, more bits of precision for note frequency, volume control, envelope frequency, and a much more configurable noise generator."

Van Grauw

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03-06-2021, 13:26

The mode select bits indeed triggers the enhanced mode if you write a specific value to it.

See the application manual for all the deets.

Van jltursan

Prophet (2520)

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03-06-2021, 13:41

Yep, seems that you switch to enhanced mode setting it with "1010" or "1011" values. Otherwise, you're in compatible mode.