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General: an APU is
Accelerated Processing Unit
- Combines CPU and GPU onto a single die
- Best of both worlds - with some problems
- AMD Fusion is the focus of this paper
- Other APUs:
"On the Efficacy of a Fused CPU + GPU Processor (or APU) for - - PowerPoint PPT Presentation
"On the Efficacy of a Fused CPU + GPU Processor (or APU) for - - PowerPoint PPT Presentation
"On the Efficacy of a Fused CPU + GPU Processor (or APU) for Parallel Computing" Paper: Mayank Daga, et. al Presentation: Liesl Wigand General: an APU is Accelerated Processing Unit Combines CPU and GPU onto a single die Best
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General: AMD Fusion: Zacate, also known as AMD E-350
- Radeon HD 6310 GPU
- 80 GPU cores
- 1.6 GHz CPU
- 500 MHz GPU
- 2 Compute Units
/SIMD /SM
- 192 MB Memory
SLIDE 4
Amdahl's Law
- An estimate of parallel speed-up
S =
- This assumes:
○ Same processor capabilities ○ Constant Workload ○ Little or no overhead
- Underestimates
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Altered Amdahl
- S' =
- p' is the parallel fraction, assuming core capabilities vary
- p/N is gone: It's not the number of cores, it's how you use them
- Added overhead value o
○ Data transfer ○ Thread set up and rejoining
- No more handy reduction to 1/s for large N
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Tested:
- Tested against :
○ AMD Radeon HD 5870 (a good GPU) ○ AMD Radeon HD 5450 (a GPU similar to the APU)
- Tested using:
○ Bandwidth Test ○ Fast Fourier Transform ○ Molecular Dynamics ○ Scan ○ Reduction
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Results
- Data transfer benefits: Good.
- Actual processing times: So-so.
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So...
- Clearly no PCIe helps
- But:
○ Internal memory is slow ○ Small data-transfer sizes are slow Improvements needed:
- Better memory merging
- Improved on die GPU
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