Re: PSG bit resolution (was Re: ReadWav for MSX)

[Ricardo Bittencourt Vidigal Leitao]

On Thu, 27 May 1999, MkII wrote:

> 4 sound sources and you got only 4 bits??? AFAIK each PSG channel has a 4
> bit volume resolution (16 levels), so 3 channels yield 5.5 bit (16*3=48
> levels). As level 16 is reserved for EG and level 0 for mute there're
> actually 45 levels.
>

        I tried to use this 5.5 bits trick when making MUST.
Unfortunately, there's no way to change all 3 volumes at the same time,
and even the small delay of 12 clock cycles introduced by consecutive OUTs
degrade the sound... The keyboard click cannot be used together with PSG
due to the same reason.

        Some Sega Master System games do use the 5.5 bits trick, but the
PSG of the Master isn't a true AY-3-8190. Instead, it is a SN-something,
slower than our one (and also it doesn't have envelopes...)
 
----------------------------------------------------------------
Ricardo Bittencourt               http://www.lsi.usp.br/~ricardo
[EMAIL PROTECTED]  "Ricardo is subtle, but malicious he is not"


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