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Old 26th Apr 2021, 11:27 pm   #4
ortek_service
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Join Date: May 2018
Location: Northampton, Northamptonshire, UK.
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Default 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.)
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