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Date:      Wed, 15 Nov 2000 13:35:03 +0100
From:      "Karel J. Bosschaart" <karelj@wop21.wop.wtb.tue.nl>
To:        Mike Meyer <mwm@mired.org>
Cc:        questions@FreeBSD.ORG
Subject:   Re: Compatibility Modules for Linux (performance issues)
Message-ID:  <20001115133503.A91826@wop21.wop.wtb.tue.nl>
In-Reply-To: <14865.58618.338076.927242@guru.mired.org>; from mwm@mired.org on Tue, Nov 14, 2000 at 07:20:58PM -0600
References:  <110137667@toto.iv> <14865.58618.338076.927242@guru.mired.org>

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On Tue, Nov 14, 2000 at 07:20:58PM -0600, Mike Meyer wrote:
> Karel J. Bosschaart <karelj@wop21.wop.wtb.tue.nl> types:
> > > On Tue, 14 Nov 2000, Trevor Legall wrote:
> > > > What is the performance hit in running programs for example Linux programs
> > > > using a compatibility module??
> > FWIW, some time ago I did some comparison tests running the linux version of
> > Unreal Tournament (version 4.28) in Redhat 6.1 and in the linux compat mode
> > of FreeBSD, on the same machine. Since that PC also had Win'98, I did
> > the test there as well (using the Windows version of UT, of course). 
> > The results of running 'utbench.dem', in frames per second:
> > 
> > Windows'98:   15.2 FPS                                               
> > RedHat 6.1:   15.8 FPS                                                     
> > FreeBSD 4.1:  14.3 FPS     
> 
> Got a question. According to my (limited) understanding of UT-like
> things, the frame rate depends as much on the video subsystem as
> anything else. So, what was the video software in use on Linux and
> FreeBSD, and how was it configured?
>
Both Linux and FreeBSD used the Linux Glide2 driver, as available from
http://linux.3dfx.com . In FreeBSD it was installed within /usr/compat/linux.
The fact that this Linux driver works in FreeBSD is because the Voodoo2
cards do not use irq, and are accessed through /dev/io to a memory range, and
that can apparently be 'emulated' very well :-). With two Voodoo2 boards
working together (the SLI - Scan Line Interleave - configuration), the 
FreeBSD tdfx driver unfortunately doesn't work, so it's root who has to
play UT in that case.  

Configuration of the cards was pretty much the same in Linux and FreeBSD,
as I used the same defaults, except for some optimizations that were also
the same on both OS's, like a refresh rate of 60 Hz, which boosts the 
framerate as compared to 75 Hz significantly. I also did tests with lower
resolutions, but surprisingly the framerate is only affected by 1 or 2 fps.
(that's quite different from Matrox G200/G400 cards, where framerate drops
considerably when going to higher resolutions. I'm still trying to get these
cards working with UT in FreeBSD, but no luck yet.)

Karel.


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