On Tue, 2007-11-13 at 22:26 -0800, Josh Dersch wrote:
  The LAG is labeled "HAL16R8CN 8440 /
342-0251-A" so it does look like a
 custom ("HAL") chip such as what Tony was mentioning.  Guess that would
 be tough to replace, unless someone out there has the means to make a
 dupilicate.  Bah.  That'll teach me to think twice next time I think I
 know what I'm doing :). 
http://www.latticesemi.com/dynamic/view_document.cfm?document_id=102
There's not much to those chips.  I'd be surprised if you couldn't suss
out what it was doing fairly easily - assuming you had a working one!
I *might* still have a Mac Classic board or two kicking about.  I'll let
you know if I find one.
Gordon