Path: utzoo!utgpu!news-server.csri.toronto.edu!rpi!zaphod.mps.ohio-state.edu!pacific.mps.ohio-state.edu!linac!mp.cs.niu.edu!ux1.cso.uiuc.edu!stuckey
From: stuckey@ux1.cso.uiuc.edu (Anthony J. Stuckey)
Newsgroups: comp.sys.apple2
Subject: Re: speed loss
Message-ID: <1991Apr20.080839.27678@ux1.cso.uiuc.edu>
Date: 20 Apr 91 08:08:39 GMT
References: <9104181535.AA28525@apple.com>
Organization: University of Illinois at Urbana
Lines: 26

THROOP@GRIN1.BITNET ("Throop,Henry B") writes:

>[toddpw writes about RAM refreshing]

>Do other computers (Mac, IBM, for example) also suspend the CPU occasionally
>to refresh the DRAMs, or do they have a seperate coprocessor or something
>like that to do it?  While the issue of the 'actual' speed of the gs has come
>up many times, I've not heard people arguing about whether the original PC
>was 4.77, or something slightly less.

yes, they do.  this is an inherent problem of all computers.  there is 
no way that i can fathom (but then, i'm a cs, not ce major) to coprocess
this.  One thing that I have noticed is that there are _many_ utilities
for DOS machines to allow you to lengthen the period before refresh (the
manufacturer's specifications are somewhat conservative)  but I have never
seen such a thing for _any_ other machine.  (mac, amiga, II, whatever)
whyfer so??

>Does this have anything to do with why IBM systems use 9 RAM chips (for
>parity checking?) where 8 do in the gs?

nope.  not at all.  that's just a design decision.  parity ram allows
you to detect memory errors (from cosmic rays, or other sources).
-- 
Anthony J. Stuckey
stuckey@ux1.cso.uiuc.edu