Re: Looking for YMF262

From: Richard Atkinson (
Date: 1999-06-30 13:17:20

On Mon, 28 Jun 1999, Mike Naberezny 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 may certainly be a possibility.  I once wired up an old PC internal
> modem to my C64's expansion port.  All I did was provide the necessary
> voltages and a little "glue" map the onboard UART into the $DE00 space.
> Probably the biggest problem with interfacing to a Sound Blaster card
> would be writing the software.

Well the idea of a compatible implementation would be that there would
already be at least some software, Commodore's own software for the YM3526
OPL, which would be upwards-compatible with the hacked Soundblaster

Anyway, time for an update: I've succeeded in finding one YMF262 chip, in
the sound card in this computer, but unfortunately it's SMT. There is also
a YAC512 and an 071 quad op-am in SMT. Ideally I need another YAC512 and
071 to make a four channel system, but the biggest problem is desoldering

There has been some progress on the reverse-engineering front, and I can
say that the final schematic is going to surprise many people - there have
certainly been some surprises for me! The Yamaha chip's interface is a bit
odd and some might say wacky, but much of this is dictated by the presence
of both /READ and /WRITE lines on the chip. Anyway, there will be no
problem from a schematic point-of-view upgrading to an OPL3, even if the
actual soldering job is a pain in the **** !

For those of you interested in the software interface of the OPL3, here is
a very good page I found which should be used in conjuction with Yamaha's
own PDF file (YMF262.PDF)

There are also OPL2 docs at that site, though I haven't had a chance to
compare them with the usual Adlib/Soundblaster site.

Anyway, to sum up I should say that the finished OPL3 card will have 5
registers not 4 as in the PC implementation for much the same reason that
the current Sound Expander has 3 registers rather than the PC's two. (to
do with the seperate /READ and /WRITE lines) Does anyone know of any good
OPL3 music software? (with source) The easiest thing to do would be a port
from PC to C64.

Still on target for a Friday release, btw ;)


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