[ltp] glxgears on a T42 (Fedora Core 3) with ATI Mobility Radon 7500

[Marius Gedminas]

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On Thu, May 12, 2005 at 11:50:21AM -0400, David A. Desrosiers wrote:
> > BTW, on an old Thinkpad 600X running Fedora Core 3, etc., this=20
> > phenomena does not occur.  Moreover, the gears visually turn very=20
> > fast even though the frame rate is about 100 fps.
>=20
> 	What you're seeing visually is the same effect that spinning=20
> rims on a car at certain speeds will exhibit.. it will almost look as=20
> though the wheels are spinning backwards slowly, or rotating much=20
> slower forwards than is actually happening.
>=20
> 	The gears are spinning fast, but they appear to be moving=20
> slowly on your screen because it executes a full rotation before the=20
> screen refreshes to show it.

Many full rotations, actually -- laptop LCD screens update at 60 fps,
while glxgears pumps out hundreds of fps.

> 	When you cover the glxgears window partially with a terminal=20
> window, you're simply "shunting" some of that drawing output, so what=20
> remains can rotate faster. Its the same thing if you resize that=20
> window to be smaller or larger.

Another thing -- if you use some sort of dynamic clock scaling daemon
(e.g. powernowd), whenever you move a window around, the CPU usage
momentarily grows, and the daemon bumps up the CPU speed, and that in
turn causes glxgears to get a higher frame rate. =20

> 	Its doing exactly what it should be doing.=20
>=20
> 	One thing you can try is backing the bpp down to 16, and using=20
> the proper ATI or X.org 3D/GL drivers for your r300 chipset, instead=20
> of the built-in driver that Fedora provides.

I believe ATI Mobility Radon 7500 is RV250, which is fully supported by
the open-source 3D driver that comes with X.org.

Marius Gedminas
--=20
MCSE =3D=3D Marginal Computer Software Enthusiast

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