6800GT ARB_vertex_buffer_object performance

OpenGL OpenGL: Advanced Coding
1

I picked up a 6800GT a few days ago, and I’m puzzled by its VBO performance. My military viz app is running slower than on my 9700 and 9800 Pros.

Running the VBO demo from Tom Nuydens also shows that something is odd. In his demo, 9700 and 9800 Pros get about 140 to 150 MTris/s, whereas the 6800GT gets about 100 MTris/s.

I’ve tried the 61.36 WHQL drivers, and the 62.01 drivers. This PNY card didn’t come with any software. I’m going to try the 61.34 drivers that PNY recommends soon.

Does anyone have any specific driver set recommendations for this card, or are there none that support VBO well?

2

I had one (6800 of some description) on loan for a short while a month or so ago. I had some problems with glDrawRangeElements and VBO. I can’t be sure of the driver version but I think it was 61.09. I tried to report it to the nVidia guy but I’m not sure he knew what I was talking about. On mine though the problem did cause a crash.

I found my app performance increased by more than double that of the 9800 and even then may have been CPU limited. However the app makes a lot of use of shaders and wouldn’t have only tested VBO performance.

Matt

3

Moving texture coordinates into the same interleaved array as the positions and normals helped somewhat.

Previously I had an interleaved buffer object, and used normal arrays for the texture coordinates:

BindBuffer( …, mesh.vbo_interleaved );
VertexPointer( BUFFER_OFFSET( 0 ) );
NormalPointer( BUFFER_OFFSET( stride ) );
BindBuffer( … 0 );
TexturePointer( … texture_coordinates );

This worked fine on ATi, but the 6800 hated it.

Changing to interleaved everything still results in faster performance on the ATi cards.

Maybe Cass has some input?

4

Hmm, something sounds amiss. I’ll look into it.

Thanks -
Cass

5

I had a bit other values - 120M on R9800pro and 122M on GF6800GT. It was on AthlonXP 2500+, where ATI’s drivers usually slower than NV.

6

My results were on a Dual 2.8 Xeon (533), and a single 3.0C P4.

7

Tom’s VBO demo doesn’t disable v-sync programatically. After disabling it the control panel, the 6800GT reached 120 MTris/s (an increase of 20), but still far below what I expected.

8

This is just Tom’s VBO demo? Please point me to the code and I’ll pass it along to the driver team.

Thanks -
Cass

9

Thanks Cass,

The demo is at
http://www.delphi3d.net/download/arb_vbo.zip

What numbers should I be getting from this?

10

What performance are you comparing on Tom’s demo, just using standard view and windows size? Cause it seems to be fillrate limited. Just looking up so the terrain goes out of view, or by making the window smaller, the performance goes up from 150Mt/s to 215Mt/s.

11

Standard window size, same view as startup.