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Date:      Tue, 28 Oct 1997 21:13:38 -0500 (EST)
From:      Chuck Robey <chuckr@glue.umd.edu>
To:        Mikael Karpberg <karpen@ocean.campus.luth.se>
Cc:        dg@root.com, hackers@FreeBSD.ORG
Subject:   Re: Parity Ram
Message-ID:  <Pine.BSF.3.96.971028211149.11899p-100000@picnic.mat.net>
In-Reply-To: <199710290128.CAA07569@ocean.campus.luth.se>

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On Wed, 29 Oct 1997, Mikael Karpberg wrote:

> 
> [...Discussion on ECC/parity/no-parity memory...]
> 
> I seem to recall something about partiy and/or ECC memory having slower
> access rates, or something, and therefor being a bad thing preformace-wise
> but a good thing safety-wise?
> 
> I don't know where I got this, but could anyone with knowledge in the
> subject maybe enlighten me on the amount of truth behind this?

They're not slower, but it takes a smallish amount of time to actually do
the matrix math, to check each word recovered from memory for errors.  If
you had to do it by hand, you'd be astounded it can be done so quickly by
machine, but it _does_ take a little time there.  The access times the
same as other ram, it's the calculation that slows things a little.

> 
>   /Mikael
> 
> 
> 

----------------------------+-----------------------------------------------
Chuck Robey                 | Interests include any kind of voice or data 
chuckr@glue.umd.edu         | communications topic, C programming, and Unix.
213 Lakeside Drive Apt T-1  |
Greenbelt, MD 20770         | I run Journey2 and picnic, both FreeBSD
(301) 220-2114              | version 3.0 current -- and great FUN!
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