Path: utzoo!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!uunet!mcsun!hp4nl!ruuinf!accucx!jaapv
From: jaapv@accucx.cc.ruu.nl (Jaap Verhage)
Newsgroups: comp.sys.ibm.pc.hardware
Subject: Re: Refreshing RAM slooows down diskette operation? Huh?
Message-ID: <1041@accucx.cc.ruu.nl>
Date: 2 Jan 91 23:17:26 GMT
Reply-To: jaapv@accucx.UUCP (Jaap Verhage)
Organization: Academic Computer Centre Utrecht, The Netherlands
Lines: 75

A while ago, in article <995@accucx.cc.ruu.nl> I wrote:
>I've got a strange little problem - to me, that is. A while ago, I
>ftp'ed some of the RAM refresh rate-twiddling programs from Simtel.
>The idea is that by refreshing your RAM chips less often than the
>standard rate for your PC, you cut down on CPU overhead, thus
>increasing the speed at which the thing operates - seemingly, at
>least. Don't expect anything gorgeous - if speed increases by
>anything like 5 % or a bit more, that's it. Still, every little bit
>helps, and I like fooling around, so I tried. The Landmark test for
>CPU speed showed my work-based Olivetti M28, a 8-MHz AT, to start
>running at 8.5 MHz; my home-based Laser AT went from 11.6 to 12.5
>MHz. Wow! You can imagine I noticed this *instantly* in running
>applications :-). But. The Laser's 5.25" HD diskettedrive came up
>with horrendously long seek times on disks! The Olivetti had no
>problems at all. Seek times on the Laser's diskettes grew as I
>cranked up the speed of the CPU by lowering the RAM refresh rates.
>Now what *is* this?
>May be stuff for a nice little discussion. If you don't think so,
>but do have suggestions, email me and I'll summarize. Thanks for
>your time and trouble.

Reactions to this were as follows:

*****
I have experienced the same magic. Would be nice to know why this
happens.

All thougths are strictly my own.
__________________________________________________________
Mats Lordin                       
Infologics AB                     E-mail: mats@infolog.se
P.O. Box 91                       Phone int +46-8-92 20 00
S-191 22 Sollentuna               Phone fax +46-8-96 08 46
__________________________________________________________
*****
  Will you settle for wild speculation?

  WHile the hard drive is usually accessed via program control, the
floppy runs with DMA. If your DMA chip is having a hard time keeping up,
this could be the problem.

  If you have a NEAT chipset, or other configurable system, try adding a
wait state to the DMA, or slowing the bus down, as from 10 to 8 MHz.
That will slow you back down, but might be an interesting test for
information.

  I would consider running one way for floppy use and one way for normal
operation, if (a) you can really tell the diference, and (b) it's easy
to switch.
---
bill davidsen - davidsen@sixhub.uucp (uunet!crdgw1!sixhub!davidsen)
    sysop *IX BBS and Public Access UNIX
    moderator of comp.binaries.ibm.pc and 80386 mailing list
"Stupidity, like virtue, is its own reward" -me
*****
  Yup, I noticed the exact same thing.  I slowed the refresh rate so that
the floppy still performed properly, but not past.  Apparently the BIOS is
doing something that is time critical, and is based on the refresh rate.
You don't happen to have an AMI bios, do you? (it's what I have)
*****

Well ... (me again):
slowing the bus down didn't help; I do have an AMI BIOS in the
Laser. Putting back the standard refresh rate in the place where it
belongs, cures the problem and also cures my wonderful speed
increase. Doesn't look like much can be done ... I guess I'll only
muddle with the refresh rate for nightlong tasks like ray tracing
and such.
Thanks to all who responded!

-- 
Regards, Jaap.

Jaap Verhage, Academic Computer Centre, State University at Utrecht, Holland.
jaapv@cc.ruu.nl      +<-*|*->+      I claim *every*thing and speak for myself