Yesterday I was nosing around my system trying to figure out how internal
video works on my IIvx. Here's what I have learned so far:

Internal video is very strange. :)

The driver for IIvx internal video is named Display Apple Video Brazil.
It is definately(sp?) in the Roms, although most system versions include
a patched version for one reason or another. I noticed that in
ROM dumps, using the program Rommie, I can't seem to find the driver in
the resource file...This is kind of confusing since I also can't seem to
find the ADBS resource but mrg has no problem finding the ADBS resource
on the BSD side. That leaves a little bit of hope.

At first I thought that maybe the driver was purely software but I loaded
the most stripped down version of the system I could run (with no
Apple Video Brazil Driver in it) and MacsBug still reports that the
driver is there.

The puzzle continues however since the damned thing wasn't showing up in
the ROM space (0x40nnnnnn) along with .Sony, .Sound, and .EDisk. It was
mapped into or copied into a low-mem space around 0x3000 or so. Quite
disappointing. I was hoping for a nice, hard-coded, ROM address. :(

A cursory examination of the driver itself reveals that it is also bizzare.
It doesn't really seem to do anything but branch around alot. I'll have to
look at it in more detail but it really is very terse assembly code. I was
expecting to see more calls to the Slot Manager than I did. I think I saw one
call. :) That should at least make it easy to glue into the kernal (I hope!).

Even if we could get the calls to work properly from the ROMs, I'm not sure
they're 100% reliable as we've seen with the lovely IIvx video kluge.
Though, I think the IIvx designers chose to make GetMode's base address
unreliable since the IIvx's video RAM begins in a well known place.

Well, if anybody is working on internal video, I hope this helps. I'm going
to keep looking into the matter, though and if I can get my EZ Drive working
I might even be able to make some experimental kernals.

Good hunting!

_______________________________________________________________________
 Michael Zucca - mrz5149@rit.cs.rit.edu - http://www.rit.edu/~mrz5149/
 "I will choose a path that's clear. I will choose Freewill. "
  --Rush, Freewill
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