Commodore 64 SID chip type?
 

I'm looking into getting a Commodore 64 to take me back to my 'yoof' especially as I used to make music on it in a lovely 8-bit manner!

However, I have read that some machines were fitted with a 'later' SID chip which performed better with less noise. Does anybody know whether is was just fitted to the Mk2 machine or also to the Mk12 breadboard ones?

Thanks, Brian

Re: Commodore 64 SID chip type?
 

You can buy SID replacement modules for around £10 off the bay, to replace the original 6581 (/ 6551?) that may now be often failing.
And these are probably microcontroller based and probably allow a later version to be used. so could probably swap out the SID chip, as were normally socketed.

Re: Commodore 64 SID chip type?
 

The Commodore 128 I had managed to get through 2 SIDs in the time I owned it.

I was lucky to source spares from someone on a TV chat room & a C64 I bought second hand.

Re: Commodore 64 SID chip type?
 

A quick Google finds an old discussion about the SID IC versions, where there are conflicting views about which version is better: https://www.lemon64.com/forum/viewto...3b087faf4e8827

However, these webpages give a lot more detail about the various versions, and the date-ranges (which overlapped!) that the various IC's were produced (as well as info on the various replacemnet modules, plus part-faulty SID IC's being sold that may have noise faults!):
https://www.c64-wiki.com/wiki/SID
https://en.wikipedia.org/wiki/MOS_Technology_6581


So the main versions seem to be:
a. Original 6581 NMOS (and various R1,2,3,4 revisions) version,
b. The uncommon 6582 / 6682A
c. The later 8580 HMOS version of it
- (Which seems to have 9Vdd rather than 12Vdd, so may not be able to swap to later one)

Whilst it would seem that all original C64 Mk1 'Breadbin' versions used the 6581, it's a bit more complicated for the later re-styled C64C version as well (as the C128). As it seems that these use both the original 6581 and the 8580 in the later versions, with the info saying:

"The better manufacturing technology in the 8580 used in the later revisions of Commodore 64C and the Commodore 128DCR caused the bias to almost entirely disappear, causing the digitized sound samples to become very quiet. Fortunately, the volume level could be mostly restored with either a hardware modification (biasing the audio-in pin), or more commonly a software trick involving using the Pulse waveform to intentionally recreate the required bias."

So you might need to open up the case to see what's actually fitted.
(And someone may always have swapped the PCB's between an original 64C and C64C to get one working (although may need to extend LED leads to do this, due to different header position etc.)

Re: Commodore 64 SID chip type?
 

Thanks for the very valuable information.

My Commodore in the past was bought in 1983 so would have had the original 6581 (no revision) by the look of things.

The later 8580 is too late to be fitted to a 'breadbin' C64 so it looks like whichever machine I go for (as I'm looking for a breadbin) it will have the 6581.

From reading the info given in the links, it sounds like all of that version chip may sound slightly different due to external forces such as capacitor tolerance rather than chip revision.

So looks like any breadbin is what I can look for and just focus on one in good condition.

Re: Commodore 64 SID chip type?
 

Yes, it does seem that all 'Breadbin' ones should have the 6581 (although maybe 1 of 4 minor revisions to it) - unless someone has swapped the board with a later C64.
And although someone may have previously-replaced the 6581 if it had failed, then it should always be another 6581 (rather than the 8580, if that is lower voltage), as it seems they carried-on making the 6581 IC many years after they started using the 8580 - presumably mainly for spares-use?

Although it would seem that all versions should normally sound OK, just that there was different software versions aimed at either the 6581 or the 8580, to compensate for differences in the DC-bias and resulting output-level (Which I hadn't been aware of until now).

But it also seems that these original IC's could be prone to partial-failure, causing sound-defects. So have to be careful if buying a replacement old-stock / used one, that may been a bit faulty. Although the new replacement FPGA etc based PCB modules shouldn't have this problem.

Re: Commodore 64 SID chip type?
 

I'm pretty certain the differences are very subtle anyway

Re: Commodore 64 SID chip type?
 

I've recently put an 'ARMSID' into my 64 and am very pleased with it. It sounds great. I just wanted to give my original a rest as they are getting a little bit more expensive and scarce now.

Re: Commodore 64 SID chip type?
 

Although it might depend on whether the original IC's would fail due to age, or being used for a long-time.
However, many Commodore IC's did run rather warm which seems to shorten their life with many ROM's (and even CPU's in C16/+4) failing quite early compared to ones in other makes.

And replacements using a much more recent standard IC, usually run significantly-cooler so should help reduced stresses on the rest of the equipment.

Re: Commodore 64 SID chip type?
 

Well I've sourced a machine and will pick it up on Thursday. Original owner has never opened the case so it will be interesting to see which revision of the SID chip (6581) it will have.

Since my original post I have managed to obtain a job lot of Commodore and other 8 bit microchips. Apart from a large number of devices used in the Commodore PET, I now have 2 off 6581 Revision 4 SID chips. Not sure if they work as I'm unable to test but at least I'll have a spare!

Re: Commodore 64 SID chip type?
 

on my c64c i got a issue the original SID literaly play the wrong octave. so i try a SwinSid and is just bad.....
and i switch to the ArmSid and since is just perfect ! and the arm sid can by teh way use the paddles and the mouse.