Re: Looking for YMF262

From: Richard Atkinson (
Date: 1999-06-28 16:24:10

On Mon, 28 Jun 1999, Nicolas Welte wrote:

> I read about the plans to upgrade the Sound Expander to use OPL2 or OPL3
> chips. The chip source would be old Soundblaster cards or compatibles.
> Why not make an interface to allow the Soundblaster card being plugged
> into the C64 expansion port? I don't think that much would be needed:
> Maybe a MHz clock source, some logic glue to convert some bus
> signals and of course the OPL2/3 address had to be mapped somewhat to
> make the SB Sound Expander compatible. As a bonus some future
> applications could even make use of the ADC and DAC on the SB card. 

This would require a schematic of the Soundblaster and/or clones and also
a deep understanding of the ISA bus, both of which I do not have. I know
that ISA has an 8MHz clock whereas the C64 uses a 1MHz clock (no, the dot
clock does not count ;). Still, if someone did hack the SB onto the C64,
maybe even making it SFX Sound Expander-compatible, it would be rather
cool. You'd have to take care of DMA transfers for the digital stuff.

> I think only old cards would work, because the newer ones have to be put
> into SB emulation mode first by some DOS program. 

Yes - the hardware registers must actually exist, rather than use
interrupts or exceptions to trap I/O accesses and execute software
emulators of the original chip.

> There are two advantages to using old SB cards: Probably many more are
> available than Sound Expanders, so many more people could use Sound
> Expander software. Also, the original C= hardware is not being hacked
> and can be kept in good condition.

The OPL->OPL2 (YM3526->YM3812) upgrade is the only _feasible_ hack for
recipients of the Sound Expanders to try. OPL3 designs are intended to be
built from scratch, so as to be compatible with Commodore's original
device but a lot easier to find the parts! Besides, an important advantage
of the home-built approach is that it can utilise the four channel feature
of the OPL3, not used by the Soundblasters. This ties in nicely with the
trend for 3D 'surround sound' in soundcards these days :)


This message was sent through the cbm-hackers mailing list.
To unsubscribe: echo unsubscribe | mail

Archive generated by hypermail 2.1.1.