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From: ford@crash.cts.com (Michael Ditto)
Newsgroups: unix-pc.general,comp.sys.att
Subject: Re: Full Height ST-506 Drives
Message-ID: <2173@crash.cts.com>
Date: 20 Dec 87 21:43:36 GMT
References: <112@lokkur.UUCP>
Reply-To: ford@crash.CTS.COM (Michael Ditto)
Organization: Crash TS, El Cajon, CA
Lines: 35
Keywords: body changes?  external
Summary: Power supply is a concern

In article <112@lokkur.UUCP> scs@lokkur.UUCP (Steve Simmons) writes:
>I'm looking at options to upgrade the 20Mb disk in my 7300.  Given
>the body, it looks like I'm stuck with using half-height drives.
>Two possible solutions spring to mind:
>
>a) Get my hands on the body molding for a 3B1, which (I think) will
>   accept a full-height disk.  Then the only issue is will the power
>   supply deal with it.  From what folks have indicated that's not
>   a problem -- back when AT&T was upgrading 7300s to 3b1s for a
>   merely ludicrous price, the power supply was not changed (er --
>   as far as anyone knows).

I upgraded the two 7300's at work to use a Seagate (ST-251, I think)
40Meg half-height drive.  It works fine, but on both systems the video
display now shrinks by about 5% for a few seconds every once in a while.
There are also slight fluctuations in the size that happen constantly.
It seems that the power supply is struggling with this drive, although
no other problems have been observed.

>b) Pursue some sort of external disk.  This would require a major
>   physical attack, but has some benefits (like I could get most
>   of the parts at cost from work).  It also solves issues of
>   power consumption (I could get a 28ms 142Mb drive if I had the
>   $$$$ -- zowie!)

Just remember that the Unix PC can only use the first 1024 cylinders
and 8 heads of the hard disk.  This means 67 Meg is the maximum size
without hardware modifications.  (If anyone knows anything about
the rumored modifications from Convergent that allow more heads or
a second drive, please post or send me mail!)
-- 

Mike Ditto					-=] Ford [=-
P.O. Box 1721					ford%kenobi@crash.CTS.COM
Bonita, CA 92002				ford@crash.CTS.COM