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Date:      Wed, 7 Apr 1999 04:01:13 +0100
From:      Mark Ovens <marko@uk.radan.com>
To:        Greg Lehey <grog@lemis.com>
Cc:        Darren Pilgrim <dpilgrim@uswest.net>, "Dragon Knight ][" <dragonknight@dtgnet.com>, FreeBSD Questions <questions@freebsd.org>
Subject:   Re: K6-2/333, was: Re: Debug kernel by default (was: System sizewith -g)
Message-ID:  <19990407040113.F4453@marder-1.localhost>
In-Reply-To: <19990407114602.Z2142@lemis.com>; from Greg Lehey on Wed, Apr 07, 1999 at 11:46:02AM %2B0930
References:  <Pine.LNX.4.04.9904051605450.10244-100000@hades.riverstyx.net> <3709569A.70EEC38A@uswest.net> <37097B00.2186EB92@dtgnet.com> <3709EDEB.BE17A2E8@uswest.net> <19990407025433.C4453@marder-1.localhost> <19990407114602.Z2142@lemis.com>

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On Wed, Apr 07, 1999 at 11:46:02AM +0930, Greg Lehey wrote:
> On Wednesday,  7 April 1999 at  2:54:33 +0100, Mark Ovens wrote:
> >
> > As the person who effectively started all this discussion about
> > bus speeds and multipliers I just want to thank all the contributors
> > to this thread. I now have a better understanding of how it all
> > works. The fundamental misunderstanding I had was that the CPU
> > itself did the mutliplication and that the m/b jumpers simply "told"
> > the CPU what multiple of the bus speed to use.
> 
> It does.  But there are various parts of the CPU.  The part which
> creates the CPU internal clock is just a bit of relatively simple
> hardwired logic.
> 

Just when you thought it was all over.....:-)

So my understanding was correct. Other posters have suggested that
the m/b supplies the multiplied clock frequency to the CPU and
therefore the it *can't* ignore it. However, whilst 95MHx & 3.5X
is equivalent to 66MHz & 5X, if the CPU doesn't understand "run at
5X" then it may be running at an arbitrary speed (3.5X bus?).

This all started when you said that you had noticed no (significant)
performance increase from a K6/233 to a K6-2/333. Whilst I'm not
disputing with you that an old HD will adversely affect performance
on disk I/O intensive work such as compiling I would expect a
noticeable performance increase overall, especially with 160MB of
RAM. This is what prompted me to ask if, whilst mathematically
equivalent, 95MHz & 3.5X was the same as 66MHz & 5X in practice
and if it isn't then that could explain the lack of performance
gain.

> > I guess that AMD only state 95MHz & 3.5X, and not 66MHz & 5X,
> > because it gives the maximum absolute performance of the chip as
> > the CPU <==> memory is running at its highest speed.
> 
> Correct.  And in fact I'd guess that you could probably choose 100
> MHz.  I've been running this chip for over a week now, and it seems to
> be fine, so I suppose it's time to start experimenting with
> overclocking.
> 
> Greg
> --
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-- 
      FreeBSD - The Power To Serve http://www.freebsd.org
      My Webpage http://www.users.globalnet.co.uk/~markov
_______________________________________________________________
Mark Ovens, CNC Apps Engineer, Radan Computational Ltd. Bath UK
CAD/CAM solutions for Sheetmetal Working Industry
mailto:marko@uk.radan.com                  http://www.radan.com



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