Just curious...

[Robert G. Brown]

Dear All,

With all the discussion of ARM and the PCI bus and other
"portable/extensible" designs, I'm curious -- has anyone ever considered
putting an interface directly on the memory bus, with its own hardware
for buffering/caching and communications?  It's probably a stupid
question, but a "shared memory extender" that is mostly transparent to
the OS on the very fast memory subsystem seems preferrable to anything
on the PCI bus, which has very definite limits on bandwidth and address
space.  I would guess that one could make do either with wait states or
with an interrupt structure to handle the speed asymmetry of the two
types of memory (real on the same motherboard and remote on a separate
one).  Something that plugged right in in place of a DIMM, but had a
whole communications interface built into it independent of any other
busses.

   rgb

Robert G. Brown	                       http://www.phy.duke.edu/~rgb/
Duke University Dept. of Physics, Box 90305
Durham, N.C. 27708-0305
Phone: 1-919-660-2567  Fax: 919-660-2525     email:rgb@phy.duke.edu