*BSD News Article 28648


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From: michaelv@iastate.edu (Michael L. VanLoon)
Newsgroups: comp.os.386bsd.misc
Subject: Re: Shared Library Status ?
Date: 14 Mar 94 08:40:02 GMT
Organization: Iowa State University, Ames, Iowa
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Message-ID: <michaelv.763634402@ponderous.cc.iastate.edu>
References: <2liu8h$6k6@u.cc.utah.edu> <CONKLIN.94Mar9160535@ngai.kaleida.com> <hastyCMGnnx.DAE@netcom.com> <michaelv.763331698@ponderous.cc.iastate.edu> <2lqck0$11k@pdq.coe.montana.edu>
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In <2lqck0$11k@pdq.coe.montana.edu> nate@bsd.coe.montana.edu (Nate Williams) writes:

>In article <michaelv.763331698@ponderous.cc.iastate.edu>,
>Michael L. VanLoon <michaelv@iastate.edu> wrote:

>>>>Earlier this week, Intel posted an announcement of 75MHz & 100MHz
>>>>clock-tripled i486's in comp.arch.  For some strange reason, Intel
>>>>calls them DX4's.
>>
>>One would hope they also increased the internal cache size.  I'm sure
>>a chip like this could potentially spend a lot of time twiddling its
>>thumbs waiting on memory.  However, knowing Intel, they probably
>>didn't think of this.

>C'mon Michael, what experience do you have developing chips?

None, admittedly.

>On-board
>cache takes up a *huge* chunk of the available space on the chip. 
>Increasing it would mean losing the FPU processor at least (which is
>what IBM did to get the speed out of their Blue Lightning).

Chip die sizes are decreasing constantly.  What wasn't possible last
year, may be possible now.  The 486 is not a new chip anymore.

>If you have fast enough secondary cache you will still see a big performance
>increase, since the 8K cache still does a fine job of fetching ~90% of the
>instructions needed.

90% sez who? :-)  90% under DOS, maybe.  I don't think a multi-tasking
OS that serves several-hundred interrupts per second and allocates
processor time between several running processes with resident memory
sets in the meg range is going to get an average 90% hit rate with an
8k cache.  I'd be pleased to be proven wrong on this point, though.

Even an external cache is going to be significantly slower than the
internal cache, since it will be running at one third the clock speed.
Granted, I very well may end up with one of these 486DX3 33/99 chips.
But, if it has an 8k internal cache, I firmly believe the performance
is going to be much less than three times the speed of a 486DX 33.
The internal cache on this chip is going to be much more vitally
important than any of its lower speed counterparts.

-- 
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 Michael L. VanLoon                 Iowa State University Computation Center
    michaelv@iastate.edu                    Project Vincent Systems Staff
  Free your mind and your machine -- NetBSD free Unix for PC/Mac/Amiga/etc.
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