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Date:      Mon, 14 Jul 1997 15:02:15 +0300
From:      Nadav Eiron <nadav@barcode.co.il>
To:        dmaddox@scsn.net
Cc:        Wes Peters - Softweyr LLC <softweyr@xmission.com>, Nick Johnson <spatula@gulf.net>, questions@FreeBSD.ORG
Subject:   Re: A few solutions
Message-ID:  <33CA1547.AD3@barcode.co.il>
References:  <Pine.BSI.3.96.970713130431.16120A-100000@pompano.pcola.gulf.net> <199707140404.WAA07219@xmission.xmission.com> <19970714072626.64852@scsn.net>

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Donald J. Maddox wrote:
> 
> On Sun, Jul 13, 1997 at 10:04:27PM -0600, Wes Peters - Softweyr LLC wrote:
> >
> > Parity RAM won't prevent errors from happening, it will just tell you
> > when they do.  The system will respond by rebooting, which really
> > doesn't get you much.  You probably just ended up with better (or faster)
> > RAM than what you had before.
> >
> > High-end UNIX workstations are often equipped with ECC RAM, which can
> > actually "fix" one-bit errors in memory accesses.  This is yet another
> > area in which garden-variety PCs don't stack up to workstations, either
> > in performance or cost.  ;^)
> >
> > Buy good quality RAM, parity or not, and be happy.
> 
> Feel free to correct me if I'm mistaken here, but I believe that there is
> no such thing as "ECC RAM".  ECC is a function of the motherboard, no?  If
> your motherboard supports ECC _and_ you have parity RAM, you can use ECC.

No. What you need is ECC motherboard and ECC RAM. To be able to correct
memeory errors you need more bits than what's available on a parity
SIMM. Some ECC implementation (the one I have in mind is the AlphaServer
1000, don't know if Pentium MBs have this too) use standard RAM, but in
greater quantity. The AlphaServer 1000 has banks of 5 standard SIMMs,
instead of the 4 that would otherwise be required for its 128 bit memory
bus. It uses the extra memory to implement ECC. Later models used 4 ECC
SIMMs instead.

Nadav



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