I was once certain, while disassembling some code, that the Egret trap was
being used to program the VIA (the Versatile Interface Adapter). The VIA is
documented in the ancient IM-III as: "controls the keyboard, internal
real-time clock, parts of the disk, sound, and mouse interfaces, and various
internal Macintosh signals".

Unfortunately, I can no longer recall the exact reasons that I had
concluded this, but you might try looking at the data structures passed to the
Egret trap to see if any of them match the VIA register and command formats
documented in IM-III pages 39-42

bryan

-----
Bryan Pendleton, Forte Software, Inc.  bryanp@forte.com  (510) 869-2138

> 
> On Wed, 9 Sep 1998, Paul Goyette wrote:
> 
> > Anyone got any idea what this trap is?  or what it does?  I've got a
> > potential SLOTMAN user with a Quadra-630, and the Q-630's ROM routine
> > for reading PRAM seems to want to invoke this trap.  My (older edition
> > of) Inside Macintosh doesn't seem to document this trap, so I don't know
> > how to emulate it or even to implement a dummy version.  :)
> 
> In Macsbug, `api a092' or `where a092' both explain that this trap is
> called "_Egret". I've never been able to figure out where it comes
> from either, but I do know that it's been responsible for a lot of
> crashes on my '630. BTW, the last time I looked, Inside Mac was available
> in PDF formt at <http://gemma.apple.com/techinfo/techdocs/mac/mac.html>
> 
>