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From: neil@mitsumi.UUCP (Neil Katin)
Newsgroups: comp.sys.amiga
Subject: Re: StepRate ... a utility that makes your floppies FASTER!
Message-ID: <453@mitsumi.UUCP>
Date: Thu, 8-Oct-87 20:06:00 EDT
Article-I.D.: mitsumi.453
Posted: Thu Oct  8 20:06:00 1987
Date-Received: Sun, 11-Oct-87 12:59:53 EDT
References: <15607@amdahl.amdahl.com>
Reply-To: neil@mitsumi.UUCP (Neil Katin)
Organization: Mitsumi Technology Inc
Lines: 46
Keywords: stepping rate improvement speedup faster floppy

In article <15607@amdahl.amdahl.com> kim@amdahl.amdahl.com (Kim DeVaughn) writes:
"Here is a really nifty utility!  It allows you to set the stepping rate
"of your floppy drives, which in turn can improve the performance of your
"system considerably!
"
"The author says he can halve the access time on his drives ... down to
"about 1500 ticks (from the stock AmigaDOS* value of 3000).  I can't get
"my old NEC drives to work that fast ... both of them will fail to read
"at 1800, but work at 1900.  So I've set them for 2000 to leave a little
"more margin (at least my old NEC's work with noKLICKstart).  Anyway,
"an improvement of 1/3 in the stepping rate is still quite noticible ...
"especially on dir listings of fat directories!
"
"I dunno if there any negative implications due to the faster stepping rates,
"such as increased wear and tear, reduced reliability, etc., so this is
"definitely a "use at your own risk" deal!  Perhaps our friends at CBM, or
"other knowledgeable disk-wise folks (Hi, Bryce!) could comment?
"
"BTW, it doesn't do anything to the "stepping rates" for vd0: or ram: ... of
"*course* I had to try it ... :-)!
"
"/kim

First of all, this "step rate" is specific to the trackdisk.device.
In 1.2 I extended the unit structure to allow people to modify some
specific device parameters (step rate, precompensation points, number
of tracks, settling time, etc.).  The worst case spec for amiga 3.5"
drives is 3 milliseconds per cylinder.  All those numbers (3000, 2000, etc)
are the number of microseconds to feed to the timer.device between
steps.

The trackdisk device is very conservative in estimating how long to delay
between step pulses.  In kickstart 1.2 on a 68000 there is a pulse every
3.7 milliseconds.  I could have tuned it for exactly three ms, but then
it would have broken on a 68020 (as others have pointed out).  Setting
your step rate to 2 ms means that you may miss some step pulses.
This typically won't be fatal -- the driver will notice that it got
a seek error and try again.

All the parameters for the unit structure are documented in the trackdisk
include file "devices/trackdisk.h".

Finally, OF COURSE the program does not work for vd0: or ram:.  The program
writes the trackdisk data directly.

	Neil Katin
	{ubvax,pyramid,amiga}!mitsumi!neil