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Originally Posted by SiriusHardware
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It gets confusing when posts are deleted
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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. |
There’s no pull up on diag, so I’m guessing it might be an output, so probably best if we don’t ask colin to short it to 0v or 5v to see what happens.