Newsgroups: can.usrgroup
Path: utzoo!lsuc!eci386!woods
From: woods@eci386.uucp (Greg A. Woods)
Subject: Re: Is it the interleave?
Message-ID: <1989Sep28.182627.25730@eci386.uucp>
Summary: not likely....
Reply-To: woods@eci386.UUCP (Greg A. Woods)
Organization: R. H. Lathwell Associates: Elegant Communications, Inc.
References: <1989Sep27.022039.14752@telly.on.ca>
Distribution: can
Date: Thu, 28 Sep 89 18:26:27 GMT
Lines: 47

In article <1989Sep27.022039.14752@telly.on.ca> evan@telly.on.ca (Evan Leibovitch) writes:
> Telly's recent disk problems supposedly provided a long-term benefit, by
> enabling me to install a Maxtor 140 Meg drive. I'm told the seek and
> transfer rates for this beast are supposed to be pretty good. The
> AT-bus controller is an OMTI, same as for the previous drive. The system
> is a 386 clone.

Does the OMTI need/have a special driver?  Perhaps their driver has a
problem with interrupts and priority levels.

Does the disk head move (i.e. you hear a click)?  Or do you hear it
re-calibrate (a whistle)?  The driver for my 3B2 misses a beat on some
of the faster drives under heavy load, and while it re-calibrates the
drive, you're stuck in very high priority driver code.  The 3B2 was
never specified to run the bigger drives, but at the same time, there
is supposed to be a fix available for this problem.

> I know that telly's  modem, on COM1:, would be radically sped up if put
> on an intelligent card. That's the next piece of hardware coming. But is
> it possible that a badly-done interleave could have this kind of effect?

The most likely problem is you're driving the serial port too fast.
It just can't keep up to that speed, and when the disk get's an
interrupt, the serial driver loses.

What you might try is to queue up a big file TO telly, and then put
uucico in debug mode (-x9) and watch the packets come in, taking
special note of those times when the disk is active.  Look for
timeouts and re-transmissions.

> What *is* the optimal interleave for a decent-speed ST506 drive?

I depends upon your CPU and controller.  If 1:1 works, use it,
otherwise you might be stuck re-formatting and testing several times
to find the optimum value.

There is also the mkfs gap factor.  This is like a filesystem level
interleave, and can be used to optimize the driver's performance.

BTW, I wouldn't call the Maxtor 1140 (it's actually 114 Mb) a screamer!
The one I have is faster than the CDC Wren 30 Mb drive though. :-)
-- 
						Greg A. Woods

woods@{eci386,gate,robohack,ontmoh,tmsoft,gpu.utcs.UToronto.CA,utorgpu.BITNET}
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