[Magic-dev] Re: Graphics performance

[R. Timothy Edwards]

Dear Michael,

> I have been doing a minor study of graphics performance.
> [...] Right now I am mainly just running glxgears on
> various Linux boxes. Some cards (like the ATI 9200 PRO) run
> OpenGL pretty quickly, other ATI cards are pretty slow.  Any
> suggestions for this?

I've stuck with Nvidia GeForce cards, which seem to be pretty fast
with Magic.  Magic itself is an excellent benchmark for OpenGL
cards and their drivers.  First, it tends to bring out all the
errors in OpenGL implementations (especially the toolbar, which
uses off-screen rendering, which has proven to be the most likely
source of error for OpenGL drivers).  Second, a large chip-size
layout can take around 10 seconds to redraw, so small differences
in performance can produce easily measurable results.

Before I wrote the OpenGL implementation, I used to have a Matrox
video card, which was the only cheap card around that supported
8-bit overlays on top of 24-bit graphics.  But Matrox lost out in
the wars with ATI and Nvidia, which was what prompted me to write
the OpenGL driver.

> This led to my noticing that use of OpenGL is normally off in
> Magic.  Would it make sense, or is there a compile option, to have
> to default on?  It appears to be possible to test for OGL at runtime.

It is theoretically possible for Magic to switch graphics drivers while
running, even to drive multiple windows with different drivers.  But
auto-detecting OpenGL seems to be a good idea.  What's the best way to
do the auto-detection?  Is it possible to differentiate between hardware
accelerated OpenGL and a software emulation like Mesa?  This has been
the main reason I haven't made OpenGL the default---it is certainly
preferred if it's hardware accelerated, but nobody would want to wait
around for the redraw of a chip using software-emulated OpenGL calls.

I'm CC'ing this message to magic-dev so that others can weigh in on the
graphics card/OpenGL issue.  There are a lot of graphics cards
available, and I only own a couple myself.

					---Tim

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| Dr. R. Timothy Edwards (Tim)   | email: tim at opencircuitdesign.com    |
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