Path: utzoo!utgpu!jarvis.csri.toronto.edu!mailrus!tut.cis.ohio-state.edu!rutgers!mcnc!rti!xyzzy!giants!poirier
From: poirier@giants.dg.com (Charles Poirier)
Newsgroups: comp.sys.amiga
Subject: Re: Hard Drive & Chip Contention
Summary: No bull
Message-ID: <4573@xyzzy.UUCP>
Date: 27 Mar 89 19:16:06 GMT
References: <16061@cup.portal.com> <8903232240.AA05683@yorkville.csri.toronto.edu> <19314@srcsip.UUCP>
Sender: usenet@xyzzy.UUCP
Reply-To: poirier@dg-rtp.dg.com (Charles Poirier)
Organization: Data General Corporation, Research Triangle Park, NC.
Lines: 50

In article <19314@srcsip.UUCP> carpent@coltrane.SRC.Honeywell.COM (Todd Carpenter) writes:
>In article <8903232240.AA05683@yorkville.csri.toronto.edu> drz@csri.toronto.edu (Jerry Zarycky) writes:
>|   There is no problem until there is a problem, and EVERY problem
>|   is a BIG problem.  When one of these screens comes up, a picture
>|   that would take a few (< 5) seconds to load, now takes MINUTES to load,
>|   with the hard disk controller LED on SOLID, with the drive making a
>|   steady noise. (To be fair, I'm not sure how many minutes it takes to
>|   load, since I abort it before it has a chance to finish).
>|   [stuff]
>
>Bull!  Excuse me, but I've been viewing *lots* of 640x400 pictures, overscan,
>and others.

You haven't said if your pictures are 4 bitplanes or not.  This is an essential
ingredient.  I'll grant, though, they probably are 4 planes.

> NO WAY does this cause slowdown on the order of minutes.  You have
>some screwy software, I think.  Yes, I get slowdown.  Probably about a factor
>of 2 to 5, at MAX.  I never exactly timed it but, I get a load of a high
>res screen in less than one second.  If there is already a high res picture up
>there, and I load in another, it is maybe 3 - 5 seconds.

I timed it.  A 27Kbyte, 640 x 400 x 4 image loads into DPaintII in 4.5 seconds
with Workbench in front, or in 45 seconds with DPaintII in front.  Extrapolate
to a more complex (less compressed) image and that easily enters the "minutes"
realm.

>I have a *fast* disk.  Other disks may not be able to handle the rate.  But I
>would think that would make the problem *less* apparent.

Not so.  The problem is that the disk overruns the 2090's tiny little buffer.
The faster the disk, the more likely the overrun.  Case in point, my older
Miniscribe (68 ms) drive had no noticeable problem, but my Quantum Q280
(28 ms) has the abovementioned severe problem.  BTW, I am using a 2090 not
a 2090A, but I was assured the buffer sizes are equal.  Given that some people
with fast drives are having little trouble, it seems that the amount of
slowdown depends on the detailed timing of the drive and not just its
"average" speed.

>Perhaps your memory is fragmented, and you are seeing garbage collection
>effects?  Or something?

No.
A)  It works identically bad from a cold, unadorned boot.  (^D as soon as
	disk is accessable)
B)  The Amiga (the sans MMU version anyway) does not page, swap, thrash,
	or garbage collect.
C)  If you meant the disk is fragmented, I think that's not it either.

	Cheers,
	Charles Poirier