Non-Standard Disks for 3B2/400

[Greg A. Woods]

In article <1990Dec10.072439.7591 at cavebbs.gen.nz> clear at cavebbs.gen.nz (Charlie Lear) writes:
> I have been very kindly offered a Seagate ST4096 to replace it. Obviously
> it has a larger capacity and different geometry from the CDC. Therefore it
> is not supported directly by the firmware.

The 3b2 firmware doesn't directly support any drives in particular.
There is a drive type field in the vtoc, but so far as I can tell, it
only tells prtconf and perhaps dgmon to spit out some arbitrary thing.
The only thing the firmware does is to assume it can find a vtoc on
every drive.  I used type 11 for the Maxtor 1140, and prtconf
magically showed a "135 Megabyte Disk".  I found that out by trying
several different types on my second drive, re-booting to check what
each type showed.

> Running SysV 3.2 and using a current idtools disk, would I be able to 
> format it to 80MB or would I have to de-rate it to 925 cyls and call it
> a CDC?

Just tell idtools the true geometry of the disk, and off you go!

Actually, since I'm not familiar with the ST4096 drive, and I can't
find my list of parameters, be careful about formatting beyond 1024
cylinders.  I don't think there's a problem with the driver handling
more than 1024 cylinders, but I can't look at the header files just
now either.  ST-506 limits you to 15 heads, of course.

Remember to use 512 byte sectors, and 18 s/track (since that's not
really part of the geometry, but rather a controller parameter, though
it does utilise the maximum number of bits per track allowed by the
ST-506 standard recording format).  You could get slightly more
formatted storage by useing 1kb sectors, but I wouldn't recommend that,
and it doesn't really gain much either.

> Please post; I'm interested in any experiences people have had in putting
> non-ATT-listed disks in 3B2's. I saw a thread a month or so back about 
> using a Maxtor XT1140 120MB disk, but didn't pay a lot of attention as the
> New Zealand list price for an 1140 is NZD$5546 (USD$3383). For those bucks
> I would rather write off the 3B2 and buy a 600MB disk and 16-port card
> for my 386... nahh, I couldn't write off the 3B2. I'd rather keep it going
> and reduce the 386/iX mob to inCoherent rage... 8-)

Yup, that was probably me.  I have/had a pair in my 3b2/400 (which has
been reduced to little more than slage by lightning), and they seemed
to work fine, though they excersise the id(7) driver heavily (it
misses the odd interrupt, and has to re-cal the drive, and there is a
partial fix available).

Well, I don't think the 1140's are that much any more, but yes, the
last time I saw a list price, they were ~$4,000(CDN).  I recall that
they were ~$7,000(US) when first announced.  Anyway, I bought my first
one surplus (but new) for a mere $700 about 3 years ago!  They are a
little more common on the used markets these days, since not many
people who want big (only 120Mb formatted!) drives are still using
ST-506.

Of course you can always get a SCSI host adapter, 3.2.{1|2|3}, and
then buy some SCSI disks!  Just don't upgrade that 386!  :-)
-- 
							Greg A. Woods
woods@{eci386,gate,robohack,ontmoh,tmsoft}.UUCP		ECI and UniForum Canada
+1-416-443-1734 [h]  +1-416-595-5425 [w]  VE3TCP	Toronto, Ontario CANADA
Political speech and writing are largely the defense of the indefensible-ORWELL