Apple Mouse Card PIA chip

Looks like it is. It says at the bottom:

Replacement for Motorola/Freescale / Rockwell / AMI / MOS Technology / MOSTEK / HITACHI / ST Microelectronics / GTE / CMD, 6520, 6521, 6820, 6821, PIA′s

and mine is AMI S6821P:

AppleMouse.jpg

Pins and functionality is compatible - as the datasheet says. But the 6521 differs in electrical characteristics. It comes in two variants - "N" and "S". The "S" variant is able to drive much higher loads. If CVT's board used the 6821, then I would try the "N" variant if possible (since the 6521N is specifically meant as a drop-in replacement for the 6821). The "S" type will probably also work (but it has no current-limiting resistors at its output ports, so is able to drive higher loads but might be more easily damaged).

The 6521 can be clocked at up to 14 MHz. It will be pretty bored with Apple II's 1MHz bus... :) But it should work...

Moreover, Jameco has this 6521 PIA in stock at $12.95.

Their copy of the Rockwell R6521 datasheet explicitly says "Direct replacement for NMOS R6520 or MC6821 PIA."  But Jameco doesn't identify which brand they're selling, so their inventory might not be the Rockwell part.

Funny thing...I saved a couple of them from a defunct Commodore PET, and I'm really not sure why.  Back in the 80's these were easily obtainable in Jameco's distinctive yellow cardstock packages for about $4.  So why did I bother keeping these pull-outs of unknown quality?

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You can buy 6520A for $1.95 each at Anchor Electronics in Santa Clara. All my Apple-1 kits used that source. These came out of Atari and never left the USA. They are marked with "6520A" and "CO14795-12" which is the Atari house marking. They were made in the early 1980s by either Synertek or Rockwell (specify when you order). Anchor also has lots of 6502B with the Atari house marking "CO14377" in stock, made by MOS Technology in the late 1970s. For $4.95 they are a steal.  Anchor also has most of the 74xx and 74LSxx used in the Apple-1 and Apple II at very good prices (the best prices I found anywhere).

www.anchor-electronics.com

- Uncle Bernie

UncleBernie wrote:

You can buy 6520A for $1.95 each at Anchor Electronics in Santa Clara. All my Apple-1 kits used that source. These came out of Atari and never left the USA. They are marked with "6520A" and "CO14795-12" which is the Atari house marking. They were made in the early 1980s by either Synertek or Rockwell (specify when you order). Anchor also has lots of 6502B with the Atari house marking "CO14377"

Very nice, I just ordered some PIA and SIO ICs from there.