AMD A10 the infernal hashing Hellraiser? - page 2.

ssateneth

legendary

Activity: 1344

Merit: 1004

Quote from: rjk on May 21, 2012, 12:12:04 PM

Now why would CPU+GPU be lower than just GPU by itself? Seems odd.

Because the Trinity modifies clocks on the fly the be within TDP. If you use CPU only, it runs CPU at full (or higher) speed. Same with the GPU. if you use both at the same time though, they both run sort of in the middle as far as speed goes

Ilikeham

full member

Activity: 238

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I get 98 MH/S from the A8-3870 @ 900 MHz with DDR3 @ 1866 and that's a Llano with Stars cores and the old 5xxx version of the GPU architecture. I'd expect this to do better at same frequency. No I don't mine on it day in and day out, I just use it as a benchmarking tool to figure out where things are at.

It's not just a question of thermal throttling, Even the new tweaked piledriver memory interface is affected by the limited bandwidth available by sharing a memory controller with the CPU cores and GPU cores. I mean in comparison to a 7750 with GDDR5 it just isn't going to get all the bandwidth it can use if the CPU cores are active as well even at DDR3 2000 as there just isn't enough bandwidth for the GPU alone, never mind the CPU's.

Still they are fun little chips to play with... think about it, for 100 ish bucks you get a nicely capable processor and light game friendly GPU that gobbles up the HD 4000 for breakfast.

Personally I stuck 6870's on the board and leave the integrated beavercreek idle for a friendly desktop interface. Power management is excellent on these.

DeathAndTaxes

donator

Activity: 1218

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Gerald Davis

Quote from: rjk on May 21, 2012, 12:12:04 PM

Now why would CPU+GPU be lower than just GPU by itself? Seems odd.

Thermal throttling. Both AMD and Intel use speedboost. As long as core is under TDP it will ramp up the clock of core(s) dynamically.

Speedboost has now been extended to GPU core too. The whole package (CPU + GPU) has a thermal limit. Using only the GPU (CPU mostly idle) creates headroom which allows "speedboost" to run the GPU faster.

Still I wouldn't say the results are fantastic. Performance looks to be ~ 1.6x the A8-3500. Not sure what a A8-3500 gets mining but the A8-3850 gets ~60 MH/s. So we are talking about 80MH/S to 100 MH/s.

oldDirty

full member

Activity: 182

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roundhouseminer

Quote from: rjk on May 21, 2012, 12:12:04 PM

Now why would CPU+GPU be lower than just GPU by itself? Seems odd.

+1
I thing it's because of memory interface/bandwith.

rjk

sr. member

Activity: 448

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1ngldh

Now why would CPU+GPU be lower than just GPU by itself? Seems odd.

oldDirty

full member

Activity: 182

Merit: 100

roundhouseminer

The first Test are out and this looks fantastic;

So i think a lot of people are going to love this new AMD Piledriver Generation.

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