AT&T 3B1 / 7300 / UNIX PC: Boot sequence from floppy

[Tony Duell]

> I'd also really like to know why the DMA controller has two separate
> direction control bits -- DMAR/W- and IDMAR/W-... this seems downright
> silly, though in keeping with the rest of the TechRef. My "annotated
> edition" corrects about a dozen minor and major errors in the register
> set descriptions, and adds a bunch of informational sticky-notes and
> scribbly comments to reinforce certain points. Ewwww...

I know nothing about this machine, but I seem to rememebr that the 
scheamtics on bitsavers contain things that appear to be the schematics 
of the DMA and video ASICs in terms of TTL parts. If I am right, that may 
be a start in understanding what they actually do.

-tony