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CBM PET 3032 STRANGE BOOT

Nivag Swerdna said:
The purists probably crave old unreliable MOS hardware but IMHO 6520s should be consigned to history. Even the most obvious replacement a 6821 is a bit obsolete.
W65C21N6TPG-14 is the way to go; order yourself some stock!

6520 -> W65C21N6TPG-14
6522 -> W65C22N6TPG-14
Click to expand...
Nivag i inserted a new 6821 instead the old 6520!
 
dave_m said:
When ordering the Western Design Center part, make sure to specify the N-MOS compatible part 40-pin DIP as Nivag has listed. It has to do with drive capability I think.
Click to expand...
  • The W65C21N is plug replacement of NMOS 6521 and 6821 devices with current limiting resistors on outputs ports and TTL input thresholds.
 
When I was restoring my AIM-65 computer I went nutty over spare parts for it, and bought all the IC's, spare displays, spare printer units power supply etc etc (that darn spare parts disease I have), including Rockwell R6520's all of which were new old stock and all work perfectly and also some SYS6520's were also good. I'm not sure if the R6520's are NMOS or not.

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Hugo Holden said:
including Rockwell R6520's all of which were new old stock and all work perfectly and also some SYS6520's were also good. I'm not sure if the R6520's are NMOS or not.
Click to expand...
Hi Hugo,
I was working at North American Rockwell (later Rockwell International) when we became the first second-source to MOS Technology on the 6502 family of parts. The R6520 was NMOS, and later the R65C21 was CMOS N-well silicon gate technology which was compatible with the NMOS parts (not sure of total drive capability).

We had a close relationship with Commodore who provided the schematics for the PET 2001-8 computer when they came out as Rockwell provided PET's at cost to any engineer in their Electronics division that wanted one for home in order that they might get familiar with the 6502 line. That is how I got my first PET in 1978. They did the same thing when Rockwell produced the AIM single board computer. My Avatar/logo on this forum is of the great predecessor company, North American Aviation which built the P-51 Mustang of WWII.
 
dave_m said:
Hi Hugo,
I was working at North American Rockwell (later Rockwell International) when we became the first second-source to MOS Technology on the 6502 family of parts. The R6520 was NMOS, and later the R65C21 was CMOS N-well silicon gate technology which was compatible with the NMOS parts (not sure of total drive capability).

We had a close relationship with Commodore who provided the schematics for the PET 2001-8 computer when they came out as Rockwell provided PET's at cost to any engineer in their Electronics division that wanted one for home in order that they might get familiar with the 6502 line. That is how I got my first PET in 1978. They did the same thing when Rockwell produced the AIM single board computer. My Avatar/logo on this forum is of the great predecessor company, North American Aviation which built the P-51 Mustang of WWII.
Click to expand...

That is a very interesting and amazing account. Thank you for sharing that.

It must bring back so many memories of those times.

I get this too, sometimes, thinking back, about what happened in my younger years.

In my case, the memories come flooding back and it can be a somewhat emotional experience.
 

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dave_m said:
When ordering the Western Design Center part, make sure to specify the N-MOS compatible part 40-pin DIP as Nivag has listed. It has to do with drive capability I think.
Click to expand...

Just got round to fitting a 65C21S into my 8032-SK and a 65C21N into a 8032 at the museum and can report that both are working fine :)
 
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