"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 of both worlds - with some problems ● AMD Fusion is the focus of this paper ● Other APUs: ○ IBM CELL ○ Intel HD Graphics: Core i3, i5 and i7 contain graphics cores ○ Projects Denver: NVIDIA teaming with Windows 8

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

Amdahl's Law ● An estimate of parallel speed-up S = ● This assumes: ○ Same processor capabilities ○ Constant Workload ○ Little or no overhead ● Underestimates

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

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

Results ● Data transfer benefits: Good. ● Actual processing times: So-so.

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

References AMD Fusion; http://sites.amd.com/us/fusion/apu/Pages/fusion.aspx IBM CELL; http://www.research.ibm.com/cell/ Project Denver; http://blogs.nvidia.com/2011/01/project-denver- processor-to-usher-in-new-era-of-computing/ Intel HD Graphics; http://ark.intel.com/products/50072/Intel-Core-i5- 2540M-Processor-(3M-Cache-2_60-GHz) Error; http://browse.deviantart.com/?q=error% 20message&order=9&offset=0#/d196lsa