Path: utzoo!attcan!uunet!seismo!sundc!pitstop!sun!decwrl!labrea!rutgers!mailrus!uflorida!usfvax2!tscs!gerard
From: gerard@tscs.UUCP (Stephen M. Gerard)
Newsgroups: comp.periphs
Subject: Re: 1:1 interleave controllers
Keywords: hard disk controller card 1:1 interleave
Message-ID: <210@tscs.UUCP>
Date: 28 Sep 88 02:01:30 GMT
References: <241@horizon.UUCP>
Reply-To: gerard@tscs.UUCP (Stephen M. Gerard)
Organization: Total Support Computer Systems, Tampa, Florida
Lines: 73

In article <241@horizon.UUCP> kevin@horizon.UUCP (Kevin Criqui) writes:
>. . .
>hard disk controller in my 286.  I'm ready to buy a 16 bit AT controller
>and have one last question.  Is it worth the extra money to get a controller
>that can use a 1:1 interleave?
For the most part, it is better to use 1 to 1 interleave.  This, however
is somewhat dependant on you applications program.  Programs that do not
use reasonable sized disk buffers can actually run slower with lower
interleave factors.  This is due to the fact that the program goes through
a cycle of:

	1.) Read data
	2.) Process Data
	3.) Goto 1

If the task of processing the data takes longer than the gap between the
record just read and next disk record to be read, the controller is forced
to wait for that data record to come back around to the read/write head.
Commands that use decent sized buffers will perform much better with lower
interleave factors.

>My machine is a 10 MHz, 0 wait state 80286 so speed shouldn't be a problem
>(should it?).  
A 10MHz 0ws AT clone will work nicely with 1:1 interleave.

>I have also heard that you need a 28mS step drive for 1:1 to work.  Is this
>true?  I guess I've been wanting to upgrade my ST238 anyway...
The step rate and interleave factor deal with different aspects of a disk's
performance.

The step rate is the time required to reposition the disk drive's read/write
head to a different cylinder.

The interleave factor determines the amount of time the controller must
wait before it can read the next logical record from the disk drive.

Hense, we can see that the step rate determines the amount of time required
to position the disk's read/write heads to a different cylinder, and the
interleave factor determines the best possible rate in which the data on
a given cylinder can be transfered.

So to answer the question, No, you do not need a 28ms step rate to take
advantage of a 1:1 interleave factor.  However, upgrading from a ST238
is never a bad idea if possible.

>Another question comes to mind.  Has anyone tried to format a Seagate ST4096
>RLL (2,7)?  I have heard that it won't work, but they said my ST225 wouldn't
>either and it works great.
Seagate's media quality and testing methods are questionable.

When using RLL technology you are in effect increasing the density in which 
the data is stored on the drive.  I have seen many Seagate drives format just 
fine with RLL controllers only to become unbootable in a few hours.  I have 
also seen many Seagate's using MFM controllers that need to be reformatted 
much more often than higher quality drives.  

(Warning: Strong opinion coming)
The only drive that Seagate makes that I would recommend is the ST4096.
I would not however, use any Seagate drive with an RLL controller unless
it was one of their drives that is specifically rated for RLL.  They have
a model ST4144R which I believe to be an RLL rated 4096. At least the
pricing should be similar, it has the same geometry as the 4096.

Sorry for the Seagate bashing.  I have seen too many problems with Seagate
drives to feel comfortable with recommending them in general.  At least
you do not have a Miniscribe :-).

Hope that this helps, Steve

------------------------------------------------------------------------------
Stephen Gerard  -  Total Support Computer Systems  -  Tampa  -  (813) 876-5990
UUCP: gerard@tscs						...tscs!gerard
US-MAIL: Post Office Box 15395 - Tampa, Florida  33684-5395