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From: neese@adaptx1.UUCP
Newsgroups: comp.periphs.scsi
Subject: Re: <23974@orion.oac.uci.edu>
Message-ID: <283400025@adaptx1>
Date: 3 Jan 91 21:30:00 GMT
References: <23974@orion.oac.uci.edu>
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Nf-ID: #R:orion.oac.uci.edu:23974:adaptx1:283400025:000:912
Nf-From: adaptx1.UUCP!neese    Jan  3 11:50:00 1991


>/* ---------- "Seagate/CDC drive caches" ---------- */
>
>Is there any difference between the Wren-6 (94191) and Wren-7 caching
>schemes?  On quick check of the manuals, Id say no, other than the
>size (32k vs 240k).  Does the wren-7 or any other seagate drive
>do any sort of segmented caching?

There is a substantial difference.  In all previous versions of the
CDC cache implementation the cache was strictly a read ahead type, where
data requested behind the pointer in the cache caused a cache miss.
In the Wren VII, there are many levels of firmware.  Some are SCSI-1
and use the same older prefetch only algorithm.  The newer SCSI-2
versions of the drive have a segmented, min/max prefetch, and true
cache algorithm.

			Roy Neese
			Adaptec Senior SCSI Applications Engineer
			UUCP @  neese@adaptex
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