FX4320,FX6300 and FX8350 review thread

[CAT-THE-FIFTH]

Supposedly,Skyrim used some X87 stuff:

http://www.joystiq.com/2011/12/27/sk...e-performance/

This is probably why Skyboost seems to work well,and supposedly newer Skyrim patches have compiler optimisations:

http://www.rockpapershotgun.com/2012...of-skyrim-1-4/

[DanceswithUnix]

It appears to be a bit of a hyperthreading thing, actually. The hardware canucks review for 6300/4300 has a synthetic FPU test - VP8/SinJulia. The VP8 test uses SSE3, whilst SinJulia uses pure x87. All the processors except the i3s have higher scores for SSE3 than x87, but by varying degrees: the quad core AMD K10 and Piledriver parts have the biggest difference, with the K10 X6 and i5s having a fairly small difference - then there's the i3s, which are FASTER at multithreaded x87 than multithreaded SSE3

SuperPi is the classic example, but I suspect there are others out there we don't know about. It'd be an interesting bit of research. I could quite fancy taking a variety of common benchmarking tasks, and re-writing/compiling them with different level of feature support...

From the description of the tests, it looks like they do different things so really shouldn't be on the same graph?

To me it just says that SinJulia runs the fpu flat out (so it's thrashing a lot on FX4).
The VP8 test seems to have enough slack that Intel threading or AMD shared FPU can schedule a second thread with ease.

Note that on FX4300 the SinJulia is roughly half that of the FX8350, it scales with cores.
VP8 test doesn't so I expect it is bottlenecking on something else like memory throughput.

[CAT-THE-FIFTH]

Bulldozer lacks X87 hardware.

[scaryjim]

Supposedly,Skyrim used some X87 stuff:

I did wonder, given how much Skyrim favours Intel hardware. Wonder how many other popular games/applications use x87 - perhaps there's some justification in using SuperPi a a benchmark after all

[watercooled]

Well still not SuperPi as it's horribly inefficient anyway. I think PiFast also uses x87 but it's far better optimised.

[DanceswithUnix]

Bulldozer lacks X87 hardware.

Don't know where you got that from, and it seems to run x87 code just fine.

Looking at that SinJulia bench:



the 8350 has 4 FPUs in its 4 modules, so should have about as much peak performance as an 980BE. It has a bit more, which is in line with the higher clock speed.

[scaryjim]

Yeah, the FPU throughput in Piledriver looks pretty good, particularly when using modern instruction sets (where the FX4300s 2 FPUs are a match for the i3s). The i3s clearly *can't* efficiently hyperthread modern (if you can call SSE3 "modern") instructions, but can efficiently hyperthread x87 - something Piledriver can't (despite the claims that the flexFPU could handle multiple smaller instructions simultaneously).

I wonder if this is actually a dispatch or decode problem? i.e. the FPU could handle the instructions but the single decoder can't decode enough instructions to push them through the pipe...? Perhaps the AMD decoder has to do more work to decode an x87 instruction, leading to a larger disparity in performance?

It also begs the question that if theoretical throughput is actually pretty good (i.e. the 8350 with 4 FPU beating the 3570k with 4 FPU in SSE3) why doesn't that translate to better lightly-threaded performance? Or is that down to lack of int throughput? Looking at the int performance in that review the 6 int cores of the FX6300 have roughly the same throughput as the 4 int cores in the 3570...

I wish I understood CPUs better... *sigh*

[CAT-THE-FIFTH]

Don't know where you got that from, and it seems to run x87 code just fine.

Looking at that SinJulia bench:



the 8350 has 4 FPUs in its 4 modules, so should have about as much peak performance as an 980BE. It has a bit more, which is in line with the higher clock speed.

AFAIK,X87 is emulated.

[CAT-THE-FIFTH]

I have added another review which contains the FX6300.

[DanceswithUnix]

AFAIK,X87 is emulated.

To be fair, integer x86 has been emulated for some time even in the Intel chips so that isn't a game changer

It has floating point hardware, it maps instructions to use that hardware.

[fishingcat]

So good for multithreaded applications on a budget, bad for single theaded apps and gaming. The high power consumption doesn't exactly inspire trust either.