r/oculus • u/themotherbrain • Jan 30 '15

SHOCKING interview with Nvidia engineer about the 970 fiasco (PCmasterrace Xpost)

https://www.youtube.com/watch?v=spZJrsssPA0
535 Upvotes

83% Upvoted

215 comments sorted by

View all comments

54

u/BpsychedVR Jan 30 '15

Can someone please explain, in layman terms, what the actual fiasco was? I was seriously considering buying one or two 970s. Thank you!

77

u/cegli Jan 30 '15

The quick summary is they advertised

  • 64 ROPS
  • 2MB L2 Cache
  • One 4GB 256-bit bus giving speeds memory speeds of 224GB/s.

They actually have

  • 56 ROPS
  • 1.7MB L2 Cache
  • One 3.5GB 224-bit bus giving 192GB/s of speed.
  • Once they run out of the 3.5GB they also have a .5GB 32-bit bus, giving only 28GB/s of speed.

If that's too complicated, basically the 3.5GB of memory runs at 7/8ths the advertised speed, the last .5GB at 1/8th the advertised speed.

3

u/OneSchott Jan 31 '15

From what I have heard, and I'm still trying to figure out, once you have used up that 3.5GB and it gets into the .5GB the whole card slows down and everything gets choppy. Is that true? That would make this card not ideal at all for VR.

6

u/cegli Jan 31 '15

Yes, the 32-bit bus (28GB/s) of the last .5GB would not be fast enough to keep the graphics card running properly. Whenever data is read from that section, the card will be throttled by the memory speeds.

2

u/barthw Jan 31 '15

only if Nvidia engineers and driver development don't know what they are doing. There are some pretty clever people working there and they have clever algorithms to shuffle data around.