Path: utzoo!attcan!uunet!portal!cup.portal.com!thad
From: thad@cup.portal.com
Newsgroups: comp.sys.amiga
Subject: Re: 2090A and DMA (was: Re: 2000-and-1 expansion box)
Message-ID: <9670@cup.portal.com>
Date: 2 Oct 88 23:55:34 GMT
References: <1925@vu-vlsi.Villanova.EDU> <7246@well.UUCP> <10313@s.ms.uky.e
Organization: The Portal System (TM)
Lines: 29
XPortal-User-Id: 1.1001.2826

Re: Steve Beat's request for ideas addressing massive storage devices ...

Present SCSI (for example) uses 32-bits to address a logical block.  Assuming
one's block size is 512 bytes, this would permit one to "reach" 2 TeraBytes
(2^12).

Given the possibility of, say, optical media having capacities in that
ballpark within a few years, the problem is not moot.

At the MINIMUM, I see the need for 48 bits of addressing such devices; at the
least would be 32-bits for a "block" and 16 bits for a byte-offset within the
block.

As a suggestion, I would recommend contacting the (known) developers of such
large storage devices now and ask them how they expect their devices to be
incorporated and used in computing systems.

As a matter of general interest, the ANSI X3T9.2 SCSI committee operates a
BBS system dedicated to the discussion of such matters as they pertain to
ANSI standards and the manufactuers of equipment expected to be in compliance
with the standards.  The SCSI-2 standard is nearly completed (for review), and
SCSI-3 is in the planning stages.  John Lohmeyer (the Chairman of X3T9.2)
recently informed me of some exciting new developments on the horizon.  Since
CBM has a need to also be compliant with future standards, I'd recommend
applying for an account on the SCSI BBS; contact me (email) if you'd like
additional info.


Thad Floryan [thad@cup.portal.com (OR) ...!sun!portal!cup.portal.com!thad]