Am 24.08.2018 um 21:39 schrieb Le_Forgeron:
> Le 24/08/2018 à 20:51, Mike Horvath a écrit :
>> On 8/24/2018 9:51 AM, William F Pokorny wrote:
>>> james    1275    32.93     # i5-8400 @ 2.8GHz (6 cores 6 threads)
>>> cyd    789    20.38     # i7-4770 @ 3.4Ghz (4 cores, 8 threads)
>>
>> Interesting. I would have expected the bottom CPU to perform better due
>> to more threads and higher clock speed.
>>
>>
>> Mike
> 
> But nobody looks at the speed of the memory (from tomhardware website):
> * i5-8400 uses ddr4 2666
> * i7-4770 uses ddr3 1600
> 
> DDR4 2666 has a bandwidth of 21333 MB/s
> DDR3 1600 has a bandwidth of 12.8 GB/s
> 
> 12.8 vs 21.3 !
> 
> That's the advantage of the new generation.

I'm not sure that translates to much of a performance gain in POV-Ray.

The memory bandwidth limits the peak throughput under sequential read
access.

Most of POV-Ray's memory accesses are probably random access though, and
there memory latency is the limiting factor, not bandwidth.

In terms of latency, DRAM hasn't seen any noticeable improvement for ages.

Also, RAM access doesn't seem to be a bottleneck for POV-Ray anyway:
There are few applications (even computation-heavy ones) that drive CPU
temperatures quite as high as POV-Ray, indicating that the CPU spends a
lot of time doing actual work rather than waiting for data to be fetched
from memory. Presumably POV-Ray's most heavily accessed data typically
fits well within the L3 cache.

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