[sdiy] Old Computers

[Mikael Mørup]

Citat Scott Gravenhorst <music.maker at gte.net>:

> =?ISO-8859-1?Q?Johannes_=D6berg?=
> <johannes.oberg at gmail.com> wrote:
> >I (who wrote a couple of months ago about my
> semi-on-going project of
> >building a sampler/groovebox out of a industrial
> PC-on-a-card and an
> >AWE32 or GUS) am still interessted in some sort of
> collaboration; of
> >making an opensource modular "os" for this type of
> synth. If anybody
> >out there is interessted.
> >
> >Anyway, from experience, if you are using an old
> computer like a 486,
> >you'll want DMA for the sound. LPT DAC won't sound very
> good,
>
> Why?
>
> This is essentially what the AVRSYN does.  I plan to do
> something very
> similar, but I will add double buffering to eliminate the
> data skew.  I
> may go the AD660 route if I can get free samples,
> otherwise, I'll build
> it from four 8 bit latches and an R2R like Jarek's.
>
> >but
> >still, if you want something simple and mono, you can
> crank out 12
> >bits with just a simple R2R network at a reasonable rate
> IIRC.
> >However, too much processing power will go to the DAC
> service, so
> >your synth engine will suffer. Also, you can get a
> pretty good
> >multichannel MIDI interface via the LPT, which IMHO it
> is better
> >suited for.
>
> I don't see loading 2 ports and toggling a "load DAC"
> line as very much
> processing at all.  But I will find out.  I plan a DAC
> update rate of
> 44KHz using the built in programmable interrupt timer.
> This is a bit
> faster than the 31.25 KHz of the AVRSYN.
>
> The first cut will be very simple, certainly a
> mono-synth.  I will
> build it on a 5x86-133 which would seem to have between 2
> and 4 times
> the power of the AVR used for AVRSYN.
>
> I also have boxes running up to and including 500 MHz
> which I may use
> when I try to play with polyphony.
>
> My OS will be DOS (I know, I know, but I ain't changing),
> it's
> something I have and I also have both C and assembler
> tools for DOS
> based programs.
>
> All I need for this is to make a DAC dongle - and it will
> plug into ANY
> computer I have.
>
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> -- Scott Gravenhorst | LegoManiac / Lego Trains / RIS 1.5
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I had a semi old Soundblaster live card, that originally
came with only standard windows drivers, but the cards
hardware was based on an Emu chip and somebody found the
docs for the chip and wrote some low latency ASIO drivers.
Doesen't that indicate that it would be possible to write
other low level software for that card / chip ?

If i recall the ASIO drivers stopped working with Windows
2000 / NT / XP. But a 500 - 1000 Mhz Win 98 or DOS based
system would go a long way in making a decent synth ?

Mikael