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From: hunt@spar.SPAR.SLB.COM (Neil Hunt)
Newsgroups: comp.unix.wizards,comp.arch
Subject: Re: Computers: The New Generation (was: Re: Free Software Foundation)
Message-ID: <797@spar.SPAR.SLB.COM>
Date: Wed, 9-Sep-87 22:44:28 EDT
Article-I.D.: spar.797
Posted: Wed Sep  9 22:44:28 1987
Date-Received: Sat, 12-Sep-87 02:59:47 EDT
References: <1184@itm.UUCP>
Reply-To: hunt@spar.UUCP (Neil Hunt)
Organization: Schlumberger Palo Alto Research - CASLAB
Lines: 31
Xref: mnetor comp.unix.wizards:4175 comp.arch:2131

In article <1184@itm.UUCP> danny@itm.UUCP (Danny) writes:

> [...]
>    How about a computer with say, 300 Meg of RAM.  There is, also,
> [...]
>    Nevertheless, whatever else may be happening, a scoo-bah of memory
>has mucho apeal.  Comments?
>

Better make sure that it has full error correction !

On a Sun 3, I believe that you can put 28 Mbytes of mem, at which time
you should expect a parity error to be detected about once a month,
with current technology. Thus 300 Megabytes will get a soft error every
three days or so (bit of a pain !). I understand that Sun 4s will have error
*correction* hardware so that they can correct single bit (?) errors,
and thus go to larger memories without crashing too often.

Does anyone know about soft failure modes of DRAMs ? How likely
is it to find double bit errors ? With denser and denser memory chips,
one might expect that one day soon, background alpha particles will be
able to flip several adjacent bits.

By the way, my dream machine would have much more than 300 M ! Some
people here have swap discs in the 100s of M on their lispms, and
still could use more ! Also I don't know why you would have a conventional
disc to back up your DRAM. I would trust my (EC) memory more than
a disc, but do conventional type backups on an Optical WORM disc
now and then.

Neil/.