Path: utzoo!attcan!utgpu!jarvis.csri.toronto.edu!mailrus!cs.utexas.edu!tut.cis.ohio-state.edu!ucbvax!ucsfcgl!cca.ucsf.edu!wet!logic
From: logic@wet.UUCP (Henry Kwan)
Newsgroups: comp.sys.mac.hardware
Subject: Re: Quantum 105 drives (again)
Keywords: How fast?
Message-ID: <774@wet.UUCP>
Date: 16 Nov 89 09:49:56 GMT
References: <4050@ur-cc.UUCP>
Reply-To: logic@wet.UUCP (Henry Kwan)
Distribution: na
Organization: Wetware Diversions, San Francisco
Lines: 33

In article <4050@ur-cc.UUCP> carlo@cvs.rochester.edu (Carlo Tiana) writes:
>There seems to be some confusion (at least in my mind and that of a few
>others I spoke to) about the Quantum 105Mb drives' speed. Is it 19ms access
>or 12ms? The MacLand ad in the Dec 89 issue of MacUser says 19ms, while
>MacWeek's M.O. section has an ad by MacTel Technology Corp. listing them at
>12ms. I have seen both figures in other places also, but have no
>references. Does anyone know what the story is?
>Thanks,
>Carlo.
>
>carlo@cvs.rochester.edu
>
>"Oh shit, not /dev/null!!!"

This confusion is caused by the fact that Quantum hard drives have a
sophisticated 64K DisCache built into the SCSI controller.  This DisCache
affects access speed because cache hits would tend to lower the number.
Quantum officially explains it as such:

On 100% random access:  Seek rate is equal to 19 ms.

On 50% random / 50% sequential access: Seek rate is reduced to 11.7 ms
                                       due to cache hits.

So some people have gotten into the habit of refering to Quantum drives as
12 ms drives.  Of course, the reason that they do it is because 12 ms is
better than 19 ms anyday.  A bit slippery but a defendable position.

-- 
Henry Kwan                |  AppleLink: D0690
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