[comp.sys.att] Full Height ST-506 Drives

scs@lokkur.UUCP (Steve Simmons) (12/17/87)

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).

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!)

Has anybody ever done either of these?


Also, many many thanks to the folks who replied to my previous
postings on memory upgrades.  The guy who sold me my 7300 is zero
help (we're on first name terms -- he calls me Steve, I call him
*ssh*le).  The world could learn a lot from the spirit of folks
on the net.

-- 
>>> Steve Simmons, Inland Sea Software, Ltd.   ihnp4!itivax!lokkur!scs <<<
>>> 9353 Hidden Lake, Dexter, MI. 48130		          313-426-8981 <<<
>>>           "It's my computer and I'll snub who I want to."          <<<

ford@crash.cts.com (Michael Ditto) (12/21/87)

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

wtm@neoucom.UUCP (Bill Mayhew) (12/23/87)

Supposedly, it is possilbe to swap the Western Digital controler
chip which is limited to 1024 cylinders for a newer WD chip that
handles up to 2048 cylinders.  I don't know if this requires
cutting traces and adding jumpers.  Dealing with more than 8 heads
would require doing some metalwork on the motherboard most likely,
I am told.  Supposedly the two WD controllers are code-compatible,
thus all that is necessary after the hardware kludge has been done
is to go back to the diagnostics disk and reformat/repartition the
drive :-), the "all this is necessary" being tongue-in-cheek.

If anybody pulls off adding a big drive, I'd be interested in
hearing how its done too.

--Bill