6
$\begingroup$

A friend got an MSI GTX 950 2GD5T graphics card for xmas.

I said "yeah, graphics cards are super fast now, that thing probably processes 2 billion triangles per second". Then I tried to look it up to check if that was even in the right ballpark, but I was unable to find a "triangles per second" stat for that card, and actually for many cards.

Is "triangles per second" even a meaningful stat? If so, what is the approximate number for this card? (given otherwise average conditions)

$\endgroup$
2
  • 1
    $\begingroup$ 'Processes' is very vague. Is that vertex shader ops? Raterizer? Shading? All of the above? None of these are meaningful, because they have a massive scene dependence. FLOPS is kind of better, but still not great because it doesnt take into account register pressure, memory latency, etc. $\endgroup$
    – RichieSams
    Dec 28, 2015 at 16:52
  • $\begingroup$ I understand that there are all of these factors. Nonetheless, I'd be interested to know about how many triangles per second can be drawn assuming modest/reasonable/typical choices for the various factors (simple/default vertex and pixel shaders, simple lighting, big model being textured by some reasonable texture sheets). $\endgroup$
    – M Katz
    Dec 29, 2015 at 18:32

2 Answers 2

3
$\begingroup$

Yes, it's a meaningful stat: GPUs have dedicated triangle setup HW and the rate is measured in triangles/GPU clock. According to white papers available on NV's website, the 680 (Kepler) could issue one triangle per SM every other clock - with 8 SMs, this yielded 4 triangles/clock. The Maxwell white paper doesn't indicate a change in this rate per SM - the 980 has 16 SMs so, if there is really is no rate change per SM, it can produce 8 triangles/clock. While the 980 has 2048 CUDA cores, the 950 has 768, implying 6 SMs and 3 triangles/clock. The chip runs around 1 Ghz, so the 950 is probably limited to 3 billion triangles per second.

$\endgroup$
5
  • 2
    $\begingroup$ Modern cards differ from previous generation cards as they nolonger have a fixed pipeline for triangles and thus its harder to say what the rate is as it waries with conditions outside the card. $\endgroup$
    – joojaa
    Jan 20, 2016 at 6:22
  • $\begingroup$ I was worried that might be the case for NV. AMD did have a fixed triangle setup engine in Hawaii, but I wouldn't be surprised if it went away in the next architecture revision. $\endgroup$ Jan 20, 2016 at 6:39
  • $\begingroup$ Again it seems to me that you can make certain default assumptions that take a lot of the uncertainly out of what's "outside the card" for the purpose of comparing card speeds (simple/default vertex and pixel shaders, simple lighting, big model being textured by some reasonable texture sheets). But I'll take this fixed-pipeline estimate of 2 billion per second as being similar to what you'd get with those assumptions. Thanks. $\endgroup$
    – M Katz
    Jan 21, 2016 at 1:26
  • $\begingroup$ I'm going to study up on NV's white papers - I need to catch up on their architecture (I worked for AMD a few years back). Ideally, there would be be synthetic benchmarks which would help everybody understand where the bottlenecks are, but there was a long history of cheating on them... $\endgroup$ Jan 21, 2016 at 3:31
  • $\begingroup$ If it's an operation that always (or nearly always) needs to be done (and triangle set up is one such thing) then there can be large power/area/efficiency reasons for using dedicated hardware. $\endgroup$
    – Simon F
    Jan 21, 2016 at 10:31
1
$\begingroup$

In my tests a GTX 1050 can do ~1B triangles with glDrawElementsInstanced(GL_TRIANGLES, .... That's roughly 2/3 of chip clock. Arguably GL_TRIANGLE_STRIP can give you an x3 speed boost, but e.g. idtech4 only supports GL_TRIANGLES.

$\endgroup$

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.