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Slothie · 24th Feb 2021, 10:35 am

Its also noteworthy that the 6521 is an equivalent to the 6520, the 6821/6521 was introduced to correct a rare 'bug' in the design. The Western Digital WDC W65C21S claims to be a "High speed/Low power replacement for Motorola / Rockwell / AMI / *MOS Technology / MOSTEK / HITACHI / ST Microelectronics / GTE / CMD 6520, 6521, 6820, 6821 PIA’s" and is in current production.
I can't imagine a Rockwell of Synertec 6520 wouldn't work as the PET doesn't exactly highly stress the PIAs.

24th Feb 2021, 10:35 am	#173
Slothie Octode Join Date: Apr 2018 Location: Newbury, Berkshire, UK. Posts: 1,287	Re: Commodore PET 2001 Its also noteworthy that the 6521 is an equivalent to the 6520, the 6821/6521 was introduced to correct a rare 'bug' in the design. The Western Digital WDC W65C21S claims to be a "High speed/Low power replacement for Motorola / Rockwell / AMI / *MOS Technology / MOSTEK / HITACHI / ST Microelectronics / GTE / CMD 6520, 6521, 6820, 6821 PIA’s" and is in current production. I can't imagine a Rockwell of Synertec 6520 wouldn't work as the PET doesn't exactly highly stress the PIAs.