PSG upgrade with an Microchip AY8930

Par gdx

Enlighted (4642)

Portrait de gdx

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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Par JohnHassink

Ambassador (5583)

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03-06-2021, 11:45

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

Par gdx

Enlighted (4642)

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03-06-2021, 11:52

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

Par ToriHino

Paladin (721)

Portrait de ToriHino

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).

Par Grauw

Ascended (10024)

Portrait de Grauw

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.

Par gdx

Enlighted (4642)

Portrait de gdx

03-06-2021, 13:03

I must have taken the wrong page.

YM2149 registers:

AY8930 default registers:

Par mars2000you

Enlighted (5970)

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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.

Par gdx

Enlighted (4642)

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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?

Par mars2000you

Enlighted (5970)

Portrait de mars2000you

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."

Par Grauw

Ascended (10024)

Portrait de Grauw

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.

Par jltursan

Prophet (2537)

Portrait de jltursan

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.