From: del@fnx.uucp (Dag Erik Lindberg)
Newsgroups: alt.cd-rom,comp.periphs.scsi
Subject: Re: CD-Rom & Adaptec 1542b
Date: 21 Aug 92 22:20:41 GMT
Organization: I/Ovations

In <1992Aug20.211713.1@ntuvax.ntu.ac.sg> astsloke@ntuvax.ntu.ac.sg writes:

>All this aside, I have a couple of questions:

>1.   Can the AH1542B BIOS utility to format and verify thrast a disk drive. 
>When I bought my Quantum PD210S,  I naturally did this.  Well my drive

Why "naturally"?  SCSI drives are delivered logically error free, there is
normally no reason to ever format them.  The format utilities are provided
for *unusual* circumstances.

>wouldn't work properly after that.  I got the drive replaced, but they told me
>not to use the BIOS utilities as these *would* thrash the drive.   I thought
>they are talking through their hats as should the drive be killable by format 
>such as the earlier IDE drives with embedded servos, the SCSI format comand 
>*should* be disabled and not result in the actual formatting operation being 
>carried out.  But I'm still not sure about formatting drives with the Adaptec. 
>I hope someone has a clear answer on this.

Yes.  I'll see if I can make it clear to you as well.  Formatting, as I
pointed out, is an unusual thing to do to a SCSI drive.  Most of the SCSI
drives (well, at least the older ones) I have encountered required some
manual twiddling if you really wanted to format them.  Since formatting is
a very device specific operation, I guess the manufacturers think it is
ok to require any sort of special formatting sequence.  The format command
is provided for you, but you better not actually use it unless you have
the technical reference manual for the drive available.  There are often
a wide variety of modes, options, and settings controlling how a SCSI
drive performs and operates.  Formatting the drive will usually erase
the record of what settings there were.

Example:  I have a drive I obtained for practically nothing because
someone did exactly as you did:  reformatted the drive, and it didn't
work properly after that.  Acted real flakey, it did.  I got the tech.
ref.  for it, and it turned out that after a 'normal' format operation,
you had to send an additional command to the drive to cause it to lock
out the manufacturers defect list.  After crafting a SCSI command to
initialize the drive, it has been working flawlessly on my Unix box as
the primary news spool for a year and a half.

>They also claim their performance to be on par with the AH1542B.  The quoted
>price is under USD200.00  (in this country).  You do need drivers for CD ROMs
>and Tapes though (bleah).   

I am always suspicious of controller performance claims.  They make sense
under DOS (typically), but NOT in a multi-user environment.  I started out
with a WD7000FASST card for my Unix system.  Under DOS the WD card is
slightly faster than the Adaptec on typical operations, and blows the doors
off the Adaptec for certain types of operations.  However, under Unix,
performance was nearly identical for both controllers with a single drive,
at least for raw disk throughput.  However, I ran a disk benchmark (not
written by either manufacturer) that also measured CPU time used by the
controller.  On my 20Mhz 80386 the WD used 80% of the CPU during transfers,
while the Adaptec only used 40%.  I don't need to tell you what that
means for interactive performance!

Then, after adding a second drive to the system (I still run with both
controllers in the system, though I now have quite a few drives attached),
the Adaptec really came into it's own.  The Adaptec is smart enough to use
the 'connect/disconnect' mode of the drives to overlap operations between
drives, while the WD just clunks along in a linear fashion.

So, again, I am highly suspicious of controller performance claims.  At
least for multi-tasking OS's there is a lot more to disk performance than
just how long it takes to move NN bytes of data.

-- 
del AKA Erik Lindberg                             uunet!pilchuck!fnx!del
                          Who is John Galt?