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Old 27th Apr 2021, 3:07 pm   #6
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?

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.
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