Re: Differences between 8501R1 and 8501R4

From: Gerrit Heitsch <*gerrit_at_laosinh.s.bawue.de*> Date: Thu, 5 Dec 2019 11:58:56 +0100 Message-ID: <0b4b7508-c29d-c693-3981-8eb574cbf5b8_at_laosinh.s.bawue.de> · gerrit_at_laosinh.s.bawue.de

On 12/5/19 9:34 AM, fhw72 wrote:
> 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

Nice... But that raises new questions:

1) So the 8501R1 didn't have a backbias generator?

2) The 8501R4 came out in 1986, after the 264 series already ended. I 
wonder why Commodore made a new revision.

3) I see another little change in the top left corner, there is 
additional stuff on the R4 above the corner pad and the trace from the 
pad below it has been widened. There is also some rerouting in the 
bottom left corner

  Gerrit