From: michaelm AT moon DOT dataplusnet DOT com
Date: Mon, 19 Jan 1998 15:13:42 -0600 (CST)
To: Elliott Oti <e DOT oti AT stud DOT warande DOT ruu DOT nl>
cc: djgpp AT delorie DOT com
Subject: Re: Speed problems with AMD K6
In-Reply-To: <34C410BF.EB7@stud.warande.ruu.nl>
Message-ID: <Pine.BSI.3.95.980119151112.3778B-100000@moon.dataplusnet.com>
MIME-Version: 1.0
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Actually, I think all AMD K6 processors run at 60 or 66 mhz bus speed and
all Cyrix do too (except for the one that runs at 75mhz).  Thus, I would
probably suspect that it has to do either with the OS or maybe DJGPP
itself (probably software related).

On Tue, 20 Jan 1998, Elliott Oti wrote:

> Gary Smith wrote:
> > 
> > Help..
> > 
> > I have just changed my CPU from a Cyrix 6x86 P166+ to an AMD K6 166MHz, and
> > have noticed a drop in performance with programmes written using using DJGPP
> > and Allegro.  The drop in performance is in the region of 20%.
> > 
> > I have benchmarked the AMD and the Cyrix using Wintune 97, and in all the
> > tests the AMD is faster than the Cyrix. eg:
> > 
> > Floating Point Performance (MFLOPS)
> > -------------------------------------------------------
> > AMD K6 P166               98
> > Cyrix 6x86 P166+          52
> > 
> > Integer Performance  (MIPS)
> > -----------------------------------------
> > AMD K6 P166               320
> > Cyrix 6x86 P166+          250
> > 
> > Does anyone have any ideas as to the cause of the performance drop with the
> > AMD CPU ?
> 
> Could be the system bus clock speed. What speed is it running at? For
> instance, I have a AMD 486 DX4-100 ( bus speed 33 MHz) and a Cyrix 486
> DX2-80 ( bus speed 40 MHz), and the DX2-80 blits consistently faster
> than the DX4-100, despite its slower CPU ( the rest of the hardware is
> identical). I don't know what speed the AMD and Cyrix boards are
> _really_ running at ( I think the Cyrix 166+ runs at 133 MHz, with a 66
> MHz bus clock; could be the AMD system bus runs at 40Mhz ). It could
> simply be that Cyrix motherboards have better buses than AMD. 
> 
> Then again, it could be a software problem; are you running your djgpp
> progs under a different DPMI host on the AMD than on the Cyrix?
> 
> -- 
> ------------ Elliott Oti ---------------
>    ------------- http://www.fys.ruu.nl/~oti  ---------
>