Path: utzoo!utgpu!attcan!uunet!tank!shamash!nic.MR.NET!csd4.milw.wisc.edu!mailrus!cornell!uw-beaver!mit-eddie!ll-xn!vlsi!young
From: young@vlsi.ll.mit.edu (George Young)
Newsgroups: comp.arch
Subject: Solid State Secondary Storage
Keywords: ram, wafer, disk
Message-ID: <248@vlsi.ll.mit.edu>
Date: 6 Jan 89 16:25:00 GMT
Distribution: comp
Organization: MIT Lincoln Laboratory, Lexington MA
Lines: 47


Our wafer scale integration group is considering developing a new kind
of computer memory unit -- something we hope might fill in the present
gap in memory speed and price between magnetic disk and ram.

Suppose you had a unit composed of a stack of silicon wafers, maybe ten or
twenty of them.

Each wafer would contain maybe 20 to 40 megabytes of word addressable
32bit (or 64bit?) slow but very dense dynamic ram.

Each wafer should add only ~$350 to the manufacturing cost of the whole unit.

Sound like heaven?  Well, the catch is speed.  In order to get very high
density and cheap fabrication, various sacrifices are made resulting in 
access time of maybe ~10 microseconds.  So we are left with a box that is:

	capacity of a few hundred megabytes,
	word addressable,
	much faster access than disk,
	much slower than ram,
	and around the same price as disk.

It also should be smaller, lighter, and more rugged than disk.

The Question Is:  What's it good for?  How might it be integrated into 
existing computer (or other) systems?  What new systems or applications
would it make feasible?
What if we could put a little matching circuit on each wafer to support
context addressable usage?  What other sort of additional (small) circuits
would be useful in such a beast?

What do people use the current (small & expensive) ram-disks for now?

Comments, raves, dreams, musings welcome by e-mail. 
Please, this is only a PROPOSED project, no real specs exist yet, so don't
ask where you can buy one :-).

George Young,  Rm. B-141		young@ll-vlsi.arpa
MIT Lincoln Laboratory			young@vlsi.ll.mit.edu
244 Wood St.				[10.1.0.10]
Lexington, Massachusetts  02173		(617) 981-2756
-- 
George Young,  Rm. B-141		young@ll-vlsi.arpa
MIT Lincoln Laboratory			young@vlsi.ll.mit.edu
244 Wood St.
Lexington, Massachusetts 02173		(617) 981-2756