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Difference in performance of integer clusters FX8320

Question asked by nihl on Jan 22, 2018
Latest reply on Jan 23, 2018 by logic

Hello

 

I found quite...interesting thing, and Im not sure what to think about it. I have several theories but none of them fit.

 

Not long time ago I decided to use my FX-8320 to check it in XMR_STACK_CPU, mining some altcoins with CryptoNight Algorithm. I own this CPu from Q4 2012, Mildly Overclocked, as my mobo's VRM is... not great.

As far as Im aware of, this algorithm is kinda heavy on FPU (Floating point)
During optimization of caches process, I found that I have difference in using differed pair of integer clusters (aka. Cores) per module in my Piledriver CPU.

 

Using 4 thread mining, even cores 0, 2, 4, 8 affinity was giving me avg 55 H/s per core. Peak was 65.2 H/s

 

Using 4 thread odd cores, 1,3,5,7 affinity was giving me avg 80 H/s, Peak was 91.25 H/s

 

It is a bit confusing for me. Using random cores without affinity gives me just slight better score than using even Cores.

 

From what I found on google, on one of Images representing "die shot" shows, that Core2 (or Core 1 in Windows) was closer placed to Cache Unit, next to Shared L2 block. However, Block diagram don't have any traces of "better" or closer pipeline connection to cache block of additional core, so I'm not happy with this theory and don't think its linked to this.

 

Now a bit more details about machine.

 

FX 8320 "Vishera" 3500mhz @4000 Mhz (20x200) 1.35v

 

Asrock 970 Extreme4, Oced, NB 2600Mhz, HT 2600Mhz, NB 1.3v, HT 1.3v, SB 1.2v

 

DDDR3 2x4GB 1866MHz CL 9 GYS1866D364L9AS/8GDC

Kingston V300 120 GB Sata 3 (This backstabbingly crippled one)

 

OCZ ModXtream Pro 700

 

Idle CPU temp is ~40c, 4 core load (50% load) is 52-55c. Full 100% Load never exceed 62c

 


Im not sure what it exactly can mean. I recall a fact, that after first two years I had odd cores locked in windows, what I discovered by installing Parking Core Manager, so my other theory would be, Cores got degraded? But I never had it actually overheating or causing issues, and during first two years I was not loading it too much.

 

Thanks in advance for all responses and ideas

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