I bought an 1GB 8800GT to have some more memory to play with, The idea was to not have to “page” memory between the CPU and GPU, gaining performance.
I got the opposite. Same hardware configuration, and the 1GB 8800GT have much lower device bandwidth then the one with 512MB;
Gainward Bliss 8800 GT 1024MB GS;
Transfer Size (Bytes) Bandwidth(MB/s)
33554432 25982.5
Inno3D Geforce 8800 GT 512MB;
Transfer Size (Bytes) Bandwidth(MB/s)
33554432 48247.3
Note that the Gainward also is factory over clocked, but still get this very bad performance in comparison.
Is this an effect of the additional memory? Both speed and amount is a factor two, so I guess this is by design, but can someone please explain…?
Well it has been like this for a long time for graphics cards; the larger memory models generally have somewhat slower memory. Especially if it’s a very large amount of memory, or the card itself is only mid-end.
This difference is shockingly large though, so there might be some other factor in play as well. Did you compare on the same motherboard in the same slot?
Yes, same everything. I only switched GPUs between the tests. Linux driver x64 169.07 or 169.09 same.
The difference is little too close to factor 2 (especially if you calculate with that the 1GB card is factory over clocked) not raising my suspicion this is a design issue. Of course it may be a faulty card, I really don’t know.
Someone else with an 1GB 8800GT that can test?
My vendor gave me a very funny reply. “No, your both cards have the same memory bandwidth” without even looking at it, referring to some computer game site … External Image
After upgrading to the 169.09 driver, BOTH my tested 8800GT cards gets 26GB/s memory bandwidth, even the reference design with 512MB.
Ubuntu 7.10 64bit server edition, 780i chipset, Q6600 cpu, 8GB pc2-6400, no x-windows and a text console jacked into the GPU. No other cards in the computer.
Downgrading back to 169.07 gives 48GB/s again, but only with the 512MB reference design.
Is this a 169.09 bug? Can someone reproduce it? I.e. test any 8800GT with 169.09 and see what bandwidth it have?
Edit: Looks like an initialization issue. If 169.07 ever have been loaded in the running system, even 169.09 will perform good (48GB/s), but after a reboot it will drop to 26GB/s.
No, the problem was not resolved, so I replaced the 1GB card with a 512MB version. I did not manage to get any more information from neither the vendor, manufacture nor Nvidia about the origin of the problem, nor get anyone to try to repeat it. I don’t know if it was as trivial as a single faulty card, a design issue, driver bug or compatibility problem.
If you decide to give it a try, I’m interested in your results. Please also note that 8800GTS 1GB is announced soon to be released by a few manufactures.
