Hello everyone, I've been doing a lot of studying up on the Power Macintosh 6500 and Twentieth Anniversary Macintosh logic boards. I own both machines and was curious what needed to be added, removed, or moved in general to make a Power Macintosh 6500 logic board work in place of a Twentieth Anniversary Macintosh logic board or vice versa. I have attached a chart below documenting every component level difference and which side of the logic board said components can be found. I'm sure most of you know by now that by removing R207 on a Power Macintosh 6500 logic board will give you the Twentieth Anniversary Macintosh start up noise, however I was curious to also see if a Twentieth Anniversary Macintosh logic board will boot in a Power Macintosh 6500 chassis, the answer is no. It will turn on but it will not display an image at all, there is however a very faint startup noise. The reasons for this can be seen in the Gazelle Schematic (configured differently for different housings and displays). The good news here though is that if you ever need to convert a Power Macintosh 6500 logic board to work in a Twentieth Anniversary Macintosh chassis this chart should be able to document those differences and allow for a smooth way to source a new board if yours were to ever need replacement.
