Differences between 8501R1 and 8501R4

A little while ago I was asked about the differences between MOS8501 R1 and
R4.
Here are my conclusions:

1. The SYNC Pin from the 6502 (Pad #7) was moved to another location: Pad
#5.
This one is still present in the 8501R1 - but not bonded.
Compare pinout of MOS6509 and MOS6502 to see evidence that they moved SYNC
from Pad #7 to Pad #5!

2. SYNC logic was removed on 8501R4 and replaced with a back bias generator.
3. GATEIN logic (and everything else) was left untouched.

Wanna see yourself.... go here:

https://is.gd/6fcY1U




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