Mac IIci: Bus arbitration: Is there any documentation available?

[Stephen_Usher]

I'm currently trying to diagnose a Mac IIci which has been passed from retro-enthusiast to retro-enthusiast to try to repair it.

Previous people have fixed the battery damage to the point where it will bong and then turn the display black and finally crash as soon as the NuBUS select line goes low.
Given how terrible (and full of errors) the Bomarc schematics are (I found two errors just in the power control circuit) I can't really trust them.
Does anyone have details about how the bus arbitration works, especially the on-board video access to Bank A of memory?

 

[robin-fo]

Check this book: https://vintageapple.org/inside_o/pdf/Guide_to_Macintosh_Family_Hardware_2nd_Edition_1990.pdf

 

[Stephen_Usher]

Thanks

 

[Stephen_Usher]

Bother! All it says is that thr RBV signals the MPU that it wants a memory transfer but doesn't give details and the Bomarc schematics are, as usual, less than useful.

 

[trag]

A lot of the bus arbitration is going to be sort of generic 68030 bus information. Apple's documentation assumes you're already an expert at all things 68030 related (or PPC related if one is trying to understand later machines).

 

[jmacz]

@Stephen_Usher how about this one? I think it has more details on Nubus.

Designing Cards and Drivers for the Macintosh Family - Macintosh Repository

Designing Cards and Drivers for the Macintosh Family (Mac abandonware from 1987)

www.macintoshrepository.org

I don't have a direct PDF link but the Macintosh Repository has both the second and third editions in zipped PDF format in the link above.

Edit: oh, I just realized this thread is from May and just got bumped up. Anyhow, if the OP is still looking for this, might want to try this book.