Xref: news2.mv.net comp.os.msdos.djgpp:4388
From: pfrisbie AT trmx3 DOT dot DOT ca DOT gov (Phil Frisbie, Jr.)
Newsgroups: comp.os.msdos.djgpp
Subject: Re: pentium-gcc
Date: 29 May 1996 19:22:13 GMT
Organization: Italia Online
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Message-ID: <4oi855$tr9@mikasa.iol.it>
References: <31AAA608 DOT 32 AT lysator DOT liu DOT se>
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To: djgpp AT delorie DOT com
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In article <31AAA608 DOT 32 AT lysator DOT liu DOT se>, alla AT lysator DOT liu DOT se says...
>
>Today i downloaded the pentium gcc 2.7.2 
>patchlevel 19 and succesfully compiled it.
>But When i compiled a program (begining of a 
>vector graphics engine) and compiled it with
>-mpentium -O6 it actually ran slower than with 
>-m486 -O2.
>
>I don't know why. have anyone tried this with other 
>results?
>
>I have a pentium overdrive 83Mhz, isn't it exactly like
>a pentium?

Unfortunatly-No.  I am also running a 83Mhz Pentium OD, and depending on the 
application, it can be almost as fast as a Pentium 75, or about as fast as a 
486 DX4/80. The reason why this is so is that a REAL Pentium has a 64 bit bus 
to memory, but the OD has a 32 bit bus (your 486 motherboard would have it no 
other way!) So when you compile for a Pentium, the  compiler is assuming the 
cpu will fetch 64 bits per clock cycle, when in fact the OD will take 2 clock 
cycles to fetch 64 bits.

>The program i ran might not be good  for comparison, i'll
>try some other program tomorrow. Gotta sleep now.
>
>/Alexander Larsson

Good luck