Dave Huang writes:
>Does anyone know where the IWM control registers are kept, btw? I notice
>there's this low memory global at 0x1e0 called IWM, but at least on my
>660av, it's 0xffffffff. (does the AV not allow direct access to the SWIM
>or something?)

I seem to remember the 660av was one of the first (THE first?) Macs to
have DMA hardware for the floppy drive.  (Formatting a floppy without
the cursor jumping like mad was a novelty at some point.)  You could
probably download the appropriate "Developer Note" PDF from
dev.info.apple.com and confirm this.  (Most of the ones I've looked at
have block diagrams of functional units -- no useful programming info,
but enough detail to tell you which chips are used and which busses go
where.)

-- monroe
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Monroe Williams                                      monroe@teleport.com