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Comment by vardump | Hacker News Reader

Keyboard is pretty amazing for C64 preservation efforts. Perhaps lessons learned could be applied to other same era systems.

There's one part in C64 that's becoming more and more rare — the amazing SID sound chip.

I wonder whether it'd be possible to have production runs of truly new 6581 and/or 8580 SID chips. Does someone still have the old masks?

Other chips you could emulate with an FPGA. But SID is partially analog, so it's special. Some say no two SIDs sound the same.

Btw, recent C64 music demo playing off 1 MB Ocean style (= ROM) cartridge (not REU):

https://www.youtube.com/watch?v=7qxxnJVU4jQ

https://www.youtube.com/watch?v=UYAf_awh5XA

Yes, it's real. Not particularly good example of SID though, but still impressive for 1982/83 technology.

But this one does show off SID; C64 "Cubase", realtime DSP (timestretch, low/high pass filter, distortion, etc.) pretty amazing:

https://www.youtube.com/watch?v=k4GWheE4Gkw

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Well, while the sound is coming from the SID-chip, it actually is samples. The really impressive thing is that they can play samples even tough the SID-chip was not designed to play samples.

The author of "Cubase64" (Pex "Mahoney" Tufvesson) has written an interesting explanation of how it is made: https://livet.se/mahoney/c64-files/Cubase64_White_Paper_by_P...

The technique used in the two first links of parent comment, is, as I understand it, based on another work of Pex : https://livet.se/mahoney/c64-files/Musik_RunStop_Technical_D...

> Does someone still have the old masks?

You can probably reverse the masks with a microscope with a little elbow grease. Not trivial by any means, but doable by someone in a garage as a hobby.

The real question, does a fab that can work with that process still exist?

There’s an ongoing effort to understand the SID here

http://forum.6502.org/viewtopic.php?f=8&t=4150

Lots of interesting analog chip level stuff, it’s all new to me as I’ve only dealt with things at the digital level, but very interesting to see how the fabrication technology works in an analog way..

None of those digitized things really are what the SID is about though, nor do they show it off for what it really is; a synthesizer for playing 3-channel tunes like these: https://www.youtube.com/watch?v=2wbwKdV89pE

For digitized sound, the SID isn't different from something like a PC beeper.

> None of those digitized things really are what the SID is about though

Fair enough. Although cubase64 does use SID features in an innovate way.

> For digitized sound, the SID isn't different from something like a PC beeper.

C64 is way superior for playing samples compared to PC beeper. Only commonality is that it takes high amount of CPU cycles, in the linked example all of it.

A PC beeper can sound just as good, when used on a fast enough PC and the beeper output is connected to something better than the built-in piezo speaker. Even on the original IBM PC, you could make it sound almost as good by very careful optimization and close to 100% of allocation of CPU cycles, like shown at the end of the 8088 MPH demo: https://youtu.be/hNRO7lno_DM?t=6m52s

We can agree to disagree, I just don't think PC beeper can in any realistic circumstances sound as good as this:

https://www.youtube.com/watch?v=U7PF5DSpjgM

How about this? There are also plenty of DOS PC-speaker-savvy demos from the 90s on pouet.net and scene.org, but there are apparently no recordings of them on youtube without sound card configurations. Some of the late DOS games also had awesome PC-speaker support. There was also a Windows sound driver for the PC speaker in Windows 3.1 times, maybe Windows 95 as well. Basically; the faster the PC, the higher the sampling rate you can go. The sound output on Raspberry Pis and some of the cheaper USB sound cards are also very similar to having stereo PC speakers, since that's also about just dumb bit-banged PWM.

https://www.youtube.com/watch?v=dV1EMcH316s

Not bad, but that C64 demo sounds clearly better. C64 can have something between 6-8 bits of resolution per sample using a trick invented by Mahoney (https://livet.se/mahoney/c64-files/Musik_RunStop_Technical_D...).

Mostly I remember this type of sound, even at higher sample rate: https://www.youtube.com/watch?v=1fErwWtkMS4

I wrote a noise shaping PC-beeper PWM converter in the nineties, oversampling at maybe 500 kHz or so. It still sounded very tinny. (First version was without shaping, and it had an annoying high frequency pitch.)

> Basically; the faster the PC, the higher the sampling rate you can go.

Not really, io-port (outb) encounters a brick wall pretty early. So no matter how fast the CPU is, you can't toggle the speaker any faster.

Not an EE, but might an FPGA be created to mimic one?

No, not for that. Its sound characteristics are from the physical layout of the chip and the individual differences from manufacturing is more notable on old revisions of 6581 than newer ones. 8580 models sound more or less identical to each other thanks to the improved manufacturing technology.

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