Hi All, As a background task this week I did something most long time users wouldn't have expected... I bought myself an ATI card so I could test it out under Linux. The card I went for was an passively cooled Radeon HD 4670, partly to keep my office quieter, and partly to reduce the power consumption, and partly because it makes this experiment not too heavy on the pocket. So how is it going with my little foray into the Red teams world?
Suprisingly well actually ;-) Power consumption: The card is real miser when it comes to using energy, at idle my Quad i7 core system now just consume 99W. I've also moved to using an OCZ Vertex Series SDD which helps keep the power consumption down so it's not jut the 4670 doing the magic. This is pretty amazing really I have very powerful machine, capable of compiling the OSG in just minutes that just sips power. A year ago my previous Intel Quad core system was consuming twice this much energy and wasn't as fast. The idle power consumption difference between by Gefore 260 (216) and the ATI is about 45W, it's not quite in the same performance segment so not an entirely fair comparison, but since I wanted low power consumption I'm happy to trade down a little performance... Performance: I haven't yet done any strict performance benchmarking, but some quick tests have shown: Volume rendering is a particular strong point, with this lower end mid range card not far behind my Gefore 260 216. Shader performance on models like glsl_mandlebrot.osg is also very good, not as good as the 260 but not far behind. Vertex throughput is pretty good as well, but compiling VBO or display lists causes frame drops that you don't see with the NVidia card/drivers. Driver stability/quality: It's a bit of hit and miss afair, but actually does far better than I expected. Hits are - all the volume ray tracing shaders work perfectly and at good performance, snow and rain effects even work, almost all example work fine. Fails are - osgviewer glsl_confetti.osg fails with all particles dropping like stones... No pbuffer support. Several crashes. Another fail external to the OSG is that enabling desktop effects in KWin causes lots of rendering problems making it unusable. With testing I've come across some driver crashes, and so far have been able to tackle one by tweaking the OSG a little to avoid the crash. The problem I've been able to resolve is the crash due to VBO compilation that was occuring when the VBO's were created inside a display lists. The NVidia driver never had a problem with this, so didn't highlight the issue, but this ATI OpenGL driver bug has shown a light on a bug in the osg::Drawable::compileGLObjects() that had it compiling display lists even when they weren't needed as in the case when your enable VBO's. Fixing the OSG bug avoids the ATI OpenGL driver bug, and should mean lower costs in compiling VBO's and memory consumption as the redudent display list is no longer compiled. This fix is now checked into svn/trunk and OSG-2.8 branch. The fix means that I can now run: osgviewer http://www.openscenegraph.org/data/earth_bayarea/earth.ive With no crash under ATI, and with better performance too and no need to disable vertex buffer objects either :-) -- Alround the test has gone very well. Sure the drivers aren't up to NVidia's standard, but they are far better than I expected given the amount of problems that members of the OSG community have had over the years. Performance has also suprised me - it's certainly enough for most parts of my work, and the power efficiency of this particular card is stella. So far I haven't come across any show stoppers that prevent me from using the card for day to day dev work, so I will continue my test with this little ATI card and keep you updated on how things go. With the addition of a ATI card here I now have coverage of ATI (Red), NVidia (Green) but as yet no Intel (Blue) parts. The later will require buying a motherboard that has Intel onboard graphics, or patience as I'd have to wait for Larabee to come out... Cheers, Robert.
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