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Faster RAM

Posted: Sun Jan 19, 2014 7:59 am
by Lugarimo
I remember Vlad always suggesting not better CPU but faster RAM.

I tested my RAM with some benchmarks and it compared well with others on the list including very expensive ones. Here are my results

Image

I can only use 5 of the cores of my cpu now before speed stops increasing. But this benchmark shows my RAM can read and write 6 GB/s so is this not fast enough? I mean PER SECOND? For NV to benefit from the speed of all my cpu threads what kind of RAM does it need?

To denoise lets say a 240p video using all 8 cores, how many GB/s must my RAM be?

Posted: Sun Jan 19, 2014 2:43 pm
by NVTeam
240p is really small so that frames of that size may even be fully cached by the CPU. Then the RAM wouldn't be a bottleneck at all.

Try to run Optimize for something larger, like full HD or even larger. Then the memory will be critical and fast RAM will be really useful.

Vlad

Posted: Sun Jan 19, 2014 4:22 pm
by Lugarimo
No, 240p does not use all 8 cores. I have tried it. It would be interesting to know if there is a resolution that can take up all 8 of my cores though.

Posted: Sun Jan 19, 2014 4:46 pm
by NVTeam
I thought you would try 1920x1080p, not 240p?

Vlad

Posted: Mon Jan 20, 2014 2:09 pm
by Lugarimo
If even 320x240 fails to use all 8 of my cores, why would 1920x1080 be any better? 1080p also doesn't use more than 6 cores.

Posted: Mon Jan 20, 2014 2:21 pm
by NVTeam
Because 1920x1080 is larger than 320x240 and requires more memory operations?

Posted: Mon Jan 20, 2014 7:40 pm
by Lugarimo
Both 240p and 1080p fail to use all 8 of my cores so what's missing here?

Posted: Mon Jan 20, 2014 7:43 pm
by NVTeam
They may be not reaching 8 but they are not equal. 1080p optimizes to 6 cores, while 240p - to 5. Increase the frame size further, see if the cores go higher too.

By the way, are those real 8 cores or 4 real + 4 HT?

Vlad

Posted: Mon Jan 20, 2014 8:43 pm
by Lugarimo
Why 240p to 5? Why not 4 or 6?
You tell me to increase to higher resolution than 1080p? I'll try.
I have 4 real cores but 8 hyperthreaded.

Posted: Mon Jan 20, 2014 9:06 pm
by NVTeam
Because Optimize measured the actual performance of the system and found that 5 is the optimal number of cores achieving the best speed on that specific hardware. On another hardware, the number could be different.

Vlad

Posted: Tue Jan 21, 2014 6:56 am
by Lugarimo
But you said RAM is my bottleneck and that higher resolutions will use more cores but this did not happen.
If I do need faster RAM, can you be specific? What do I need faster, RAM read/write speed or lower latency?

Posted: Tue Jan 21, 2014 8:26 am
by NVTeam
> But you said RAM is my bottleneck

I remember saying the following:
> More cores will not always means more speed even on a multi-threaded program.
Agreed. Possible reasons of that are many. One of them, significant for large frames, is the limited memory bandwidth. Modern multi-core CPUs can process data faster than the memory system can deliver that data to the CPU.
Cache size is important too. If fewer cores do the work then they can use larger portions of the shared cache memory, which speeds up memory operations for those active cores. But fewer cores also means lower overall computing speed. These two tendencies compete with each other and as a result the highest speed is achieved somewhere in the middle. Generally faster memory can change the optimum. Larger cache size of the CPU can change it too. Which is why it is important to use a fast RAM and a high-end CPU with large cache memory.
Vlad

Posted: Tue Jan 21, 2014 11:36 am
by Lugarimo
Ok but what does fast RAM mean? RW speed or latency?

Posted: Tue Jan 21, 2014 11:58 am
by NVTeam
Both.

Posted: Fri Jan 24, 2014 9:43 pm
by Lugarimo
Ok and to be clear, if I got say a i7 4770 rather than my first generation i7 which is twice as slower, would I get twice the speed with NV (using the same RAM I have now)?