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From: fjo@ttrde.UUCP (Frank Owen )
Newsgroups: comp.sys.mac
Subject: Re: Making *own* SCSI Hard Drive
Message-ID: <230@ttrde.UUCP>
Date: Wed, 15-Jul-87 13:54:47 EDT
Article-I.D.: ttrde.230
Posted: Wed Jul 15 13:54:47 1987
Date-Received: Sat, 18-Jul-87 05:53:31 EDT
References: <7141@shemp.UCLA.EDU>
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>    I leafed through some non-Mac magazines, and indeed it
> looks like one can easily get a 40M Seagate sans controller
> for less than $450. This stirred considerable enthusiasm in
>   - what is your estimate of the controller's cost ($300? $50?)
You should be able to get controllers for ~$150. You may also be
able to get old surplus SASI controllers for less than this.
("Computer Surplus Store" has a bunch of SASI boards for $79.
They advertise in the back of Byte Magazine.  ph.(408)-280-1740.
You'll also need a power supply, case and cables to make
a working model.

>   - I have no idea about how the thing works, so a very stupid
>     question: would this "poor man's" controller significantly
>     affect the disk's access time, if at all?
The really cheap controllers might not be able to read disks formatted
at a 1:1 interleave. (Read entire track in one revolution). The one
I got (DTC 520) is limited to a 2:1 interleave factor. This is only
an issue if you want to use the drive on an SE or MacII, because the
MacPlus is not able to keep up with a 1:1 interleave factor anyway.
The MacII (I think) can. (Although it does NOT have a DMA for the
drive, it has a faster processor, so it SHOULD be able to keep up 
with the 1:1 data rate. )
   In most cases, however, the greater measure of disk speed comes from
the "average seek access time" of the drive itself. This measurement
pretty much determines the price of the drive in question.

>   - are there any serious drawbacks of this solution .... 
The drawbacks are that you are really on your own in terms of
getting the software working to drive your particuliar board/drive
combination. You also don't get fancy things like disk-spoolers,
and backup utilities (unless you want to spend the time writing
them yourself, or find them availible in the public domain)


Frank Owen
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