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JeGX's DevBlog
Catalyst 7.9, Radeon 2900 and Surface Deformer 
Wednesday, September 12, 2007, 09:03 AM - ATI
Posted by JeGX
From oZone3D.Net Forums, the Catalyst 7.9 seems to unleash ATI Radeon 2900 GPU. The Surface Deformer benchmark is a benchmark that requires a lot of vertex processing horse power. With Catalyst prior to 7.9, the score of an ATI 2900 was around 8000 o3Marks (that was already high). Now with Catalyst 7.9, the 2900 gets a score of 15000 o3Marks. Incredible!!! Why such a big big jump in OpenGL performance ?

My first thought is that ATI has managed to use correctly the unified arch of the R600 gpu. With unified arch, the workload is distribued over all shaders processors no matter the type of the shader prog (vertex or pixel). So if the vertex shader needs more processing power than the pixel shader, more shaders processors will be used for the vertex shader. My second thought: unified arch has involved new kernel code for catalyst and simply ATI has optimized the R600 codepath. A driver for a modern GPU like the R600 is a very complex piece of code and optimizing such a code is a huge task....


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Catalyst 7.9 and Radeon 2K Shadow Mapping Bug 
Wednesday, September 12, 2007, 09:00 AM - ATI
Posted by JeGX
I found this bug while I was coding a new small soft shadows demo for GPU Caps Viewer. Soft shadows are built on shadow mapping and my OpenGL shadow mapping code works perfectly on all Geforce 6/7/8 and Radeon 1k but not on Radeon 2K (2400/2600/2900). Why ? Because of the shadow mapping comparison function that had a serious bug! To be short, the comparison function was supposed to return a boolean value (if shadow returns 0, else returns 1) and before Catalyst 7.9, this function returned, for Radeon 2K, the depth buffer value (as if the comparison function was disabled). But this bug is now a memory since Catalyst 7.9 has fixed it.

I guess we can say thanks to Quake Wars, that has been released few days ago and that is an OpenGL game. For this game (that is really nice), ATI has fixed all major OpenGL bugs.

The Catalyst 7.9 are available here: http://game.amd.com/us-en/drivers_catalyst.aspx

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R600 is VTF-capable 
Tuesday, May 29, 2007, 09:44 AM - ATI
"All of the fetch and filtering capabilities are available to each thread type, making the samplers completely agnostic about what's using them."

This line from Beyond3D article on R600 means that vertex, geometry and pixel shaders can access to texture samplers. So Vertex Texture Fetching is now available with Radeon 2k series :thumbup: What's more, the R600 can handle very large texture up to 8192x8192 just like the G80.

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Dynamic branching and NVIDIA Forceware Drivers 
Tuesday, May 22, 2007, 12:56 PM - NVIDIA
Several weeks ago, I posted on Beyond3D a thread on my dynamic branching benchmark. I wondered why dynamic branching performances on Geforce 7 were worse than ones on Geforce 6 or 8. I believe I've got the answer: Forceware drivers.

Here are some new results where ratio = Branching_ON / Branching_OFF :

7600GS - Fw 84.21 - Branching OFF: 496 o3Marks - Branching ON: 773 o3Marks - Ratio = 1.5
7600GS - Fw 91.31 - Branching OFF: 509 o3Marks - Branching ON: 850 o3Marks - Ratio = 1.6
7600GS - Fw 91.36 - Branching OFF: 508 o3Marks - Branching ON: 850 o3Marks - Ratio = 1.6
7600GS - Fw 91.37 - Branching OFF: 509 o3Marks - Branching ON: 850 o3Marks - Ratio = 1.6

7600GS - Fw 91.45 - Branching OFF: 509 o3Marks - Branching ON: 472 o3Marks - Ratio = 0.9
7600GS - Fw 91.47 - Branching OFF: 509 o3Marks - Branching ON: 472 o3Marks - Ratio = 0.9
7600GS - Fw 93.71 - Branching OFF: 508 o3Marks - Branching ON: 474 o3Marks - Ratio = 0.9
7600GS - Fw 97.92 - Branching OFF: 505 o3Marks - Branching ON: 478 o3Marks - Ratio = 0.9
7600GS - Fw 100.95 - Branching OFF: 508 o3Marks - Branching ON: 480 o3Marks - Ratio = 0.9

my conclusion is: dynamic branching in OpenGL works fine (read the performance are better than without dynamic branching: ratio > 1) for forceware <= 91.37. For the drivers >= 91.45, the ratio drops under 1. Dynamic branching works as expected for gf6 and gf8 but not for gf7 since forceware 91.45. So the bug explanation is a plausible answer (and it's easily understandable: in this news , we learnt that a forceware driver is made of around 20 millions of lines of code - a paradise for a small bug!!!). I've also done the test with the simple soft shadows demo provided with the NV SDK 9.5. The results are the same.

I've just done the bench with a 7950gx2 and the latest forceware 160.02 and dynamic branching is still buggy...

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Dell XPS M1710 GeForce Go 7900 GTX et OpenGL 2.1 
Tuesday, May 15, 2007, 11:03 AM - NVIDIA
Vous avez un ordi portable et vous en avez marre de ces sales pilotes graphiques jamais à jour de la part des constructeurs ? C'est mon cas avec le Dell XPS M1710 équipé d'une geforce go 7900 gtx. Les derniers pilotes officielles chez Dell ou chez NVIDIA sont les 84.xx... Vu le prix d'un portable de ce type, c'est quand même honteux de leur part :thumbdown:

Mais heureusement qu'il y a des petits gars bien motivés (par exemple http://www.laptopvideo2go.com) qui bricolent les derniers pilotes graphiques pour les rendre compatibles les portables. Donc j'ai décider d'installer les Forceware 158.18 sur mon laptop sous WinXP. Voilà comment faire et c'est super simple:

1 - download des pilotes 158.19: http://www.laptopvideo2go.com/drivers/xp
2 - download du fichier INF modifié sur la même page: http://www.laptopvideo2go.com/drivers/xp
3 - décompression du driver 15819.exe dans un répertoire par exemple fw15819/
4 - remplacement du fichier INF d'origine par celui modifié
5 - lancement de l'installation de manière assez classique: setup.exe

Pour ma part cette installation s'est très bien déroulée comme le montre les deux captures d'écran de GPU Caps Viewer:





Maintenant mon laptop supporte l'OpenGL 2.1 et le GLSL 1.2 :thumbup: et surtout il est capable de faire tourner mes dernières petites démos qui utilisent le HDR, les multiple render targets, le DOF... Les images arrivent bientot :winkhappy:

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SLI is nice! 
Tuesday, September 5, 2006, 10:22 AM - NVIDIA
I must confess the SLI is a really cool technology. I assembled a SLI station based on the new nVidia Geforce 7600 GS series. This is a little graphic card compared to the high-end ones like the 7900GTX or the big monster 7950 GX2 (which in passing is really quiet in spite of its two GPUs and ventirads): the price of a 7600GS is about 100 euros, the price of a 7900GTX is about 400 euros and the cost of the 7950 GX2 climbs up to 500 euros! In terms of shader pipelines, the 7600 GS has 5 vertex pipes and 12 pixel pipes, the 7900 GTX has 8 vertex pipes / 24 pixel pipes and the GX2 has 48 pixel pipes and 16 vertex pipes. And so what? A 7600 GS SLI system offers almost the same level of gpu power than a 7800/7900 for a half price. I've verified this fact with the latest version of the soft shadows benchmark. With one 7600 GS (single GPU mode) the score is 510 o3Marks. With the two 7600 GS in SLI mode, the score jumps to 1004 o3Marks. The 7950 GX2's score in single GPU is about 1200 o3Marks. Ok my bench is a small bench, you're right. What about 3dmrk06? The 3DMark06 score is 4115 for the 7600 GS SLI system. This score is close to the ones got with a non-overclocked gf7800/7900.
Little remark: my 7600 GS are not overclocked.

Conlusion: for 200 euros you can have an excellent graphic system which is also silent thanks to the 7600GS passive cooler!





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