Path: utzoo!utgpu!news-server.csri.toronto.edu!rpi!usc!elroy.jpl.nasa.gov!decwrl!pa.dec.com!shodha.enet.dec.com!devine
From: devine@shodha.enet.dec.com (Bob Devine)
Newsgroups: comp.arch
Subject: Memory hierarchy (was: Snakebytes)
Message-ID: <2832@shodha.enet.dec.com>
Date: 27 Mar 91 22:15:07 GMT
References: <1998@kuling.UUCP>
Organization: Digital Equipment Corp. - Colorado Springs, CO.
Lines: 22

In article <1998@kuling.UUCP>, irf@kuling.UUCP (Bo Thide') writes:
> Now that the Snakes (HP9000/700 series HP-PA 1.1 RISC workstations) are let
> loose, the official HP info has become available.  Some of this info follows.
> 
> Cache: 128 kB instr/256 kB data (720, 730), 256 kB instr/256 kB data.

The sizes of the caches used in HP Snake systems are interesting.
A bit more than a decade ago (or more than 3 generations ago
if expressed in "product cycle years"), the first release of
the VAX 11/780 had a minimum main memory of 256 kB.

The memory hierarchy has, so far, be contained inside the "box"
and hasn't extended to the disks.  Disks are, for the most part,
still treated as a single-level.  Even RAIDs are made to look
like one big disk.  Some research efforts have been made to
move files off and return files to disk based upon access patterns.

My questions are to the folks with a /dev/crystal_ball: when will
two level processor caches be here?  When will a storage hierarchy
be extended to disks (or to ram-disk, or ... etc)?

in a wondering mood,
Bob Devine