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Old 16th Mar 2021, 9:30 pm   #1070
SiriusHardware
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Join Date: Aug 2011
Location: Newcastle, Tyne and Wear, UK.
Posts: 11,483
Default Re: Non-working Commodore PET 3016

Quote:
It gets confusing when posts are deleted
To stir things a bit further I believe aj (and he has just confirmed it ) knew that but was pointing out that it was referring to system RAM, not video RAM. He thought for a moment that we were still musing over a potential video RAM problem.

Having read through that doc again it sounds increasingly like it must have been supplied with a diagnostic gadget of some sort rather than using a built in 'bootloader' feature. I would be interested to know what purpose the 'diag' connection (J9 pin 20 / User port pin 5) on sheet 3 serves, and how it might be used. It goes to pin 9 of UC7, 6520, and is indicated on the diagram as being both input and output.
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