
Commodore 64 SID replacement using a Teensy 3.6 - sohkamyung
https://hackaday.com/2018/07/24/sad-without-a-sid-this-comes-pretty-close/
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mrweasel
Recently I've been watching a bunch of retro-computing stuff on YouTube, and
the restoration projects that people embark on have made me wonder how hard it
would be to reproduce the required chips?

Sure the C64 can just be emulated, and there are kit allowing you to fit a
RaspberryPi in a C64 case, and use the keyboard, but it's not really the same.

~~~
classichasclass
Part of the problem with the SID particularly is its analogue components, such
as the filter, which are very hard to simulate digitally. It's not just demos
that depend on their behaviour.

Even Commodore themselves weren't able to reproduce all of its subtleties
(i.e., the 6581 vs 8580 differences).

Bob Yannes did some amazing things with the chip, especially considering the
limitations he had to work under:
[http://sid.kubarth.com/articles/interview_bob_yannes.html](http://sid.kubarth.com/articles/interview_bob_yannes.html)

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tibbon
I do wonder what it would take to emulate it more properly on a component
level. It's definitely a "weird" filter and doesn't behave like one would
assume it to.

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opencl
You could probably emulate the analog sections with a circuit simulator like
SPICE.

~~~
8bitsrule
Analog is hard to emulate well. At least, I've never heard of a decent
emulation of the legendary Moog filter. 'Infinite' trumps 'many'

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mrob
Analog is hard to emulate because real components have complicated non-linear
and stateful behaviors, and because real circuits are full of parasitic
components, not because of "infinite" anything. Analog circuits have finite
SNR and bandwidth, and the "many" of digital can easily exceed them.

Analog circuits also tend to have high variation between units. You might have
a perfect simulation of the average hardware, but it won't necessarily sound
like your specific hardware. You'll need to measure your hardware and tune the
simulation to match. People have done this for SID chips:

[https://bel.fi/alankila/c64-sw/yourchip.html](https://bel.fi/alankila/c64-sw/yourchip.html)

~~~
8bitsrule
In music 'high variation' is frequently a plus. For example the value of
Stradivarius or Steinway (and countless other instrument brands) is dependent
on 'hard to emulate'.

Of course digital has its place ... but nature chose to go with analog.

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kokey
I've had to dispose of a Commodore 64 because the SID was dead, since it's
pointless without the sound. This is potentially quite useful.

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soegaard
SwinSID has been available a while.

[https://www.c64-wiki.com/wiki/SwinSID](https://www.c64-wiki.com/wiki/SwinSID)

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Braini
IMHO the best emulation so far is the FPGASID
([http://www.fpgasid.de/](http://www.fpgasid.de/)). There are a number of
YouTube videos where it is compared against the originals.

~~~
soegaard
Forgot about that one. But ... reservations has been closed.

[http://www.fpgasid.de/fpgasid-reservation](http://www.fpgasid.de/fpgasid-
reservation)

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8bitsrule
_real SID chips are rare as hen’s teeth nowadays_

Damn. Now I wish I'd bought that pile of used C64s stacked in the thrift shop
window that day.

 _its analogue components, such as the filter, which are very hard to simulate
digitally._

Analog's day came, went, and will be back again ... because for sound it's
just superior in -many- ways. And hacking is hardware, not software.

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mrob
What are those "many" ways? I can only think of one: it's easier to design
good sounding analog synths/effects. The imperfections get you complexity of
sound for free, and you don't have to worry about aliasing. But in a
hypothetical world where everybody is a DSP genius, I see no reason for analog
audio processing at all.

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Yaa101
Nowadays one could make or copy one of the vhdl files out there and bake it in
pretty much any form.

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asciimo
What the heck is the Commodore 54?

~~~
ComputerGuru
A typo, obviously?

