Cell processor ALU(s)

getoffb

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Jun 19, 2003
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Does the Cell Processor's SPU/SPE have an integer-based ALU?

I know that Google should turn up an answer rather quickly, but I've been searching for the better part of 5 hours and haven't found anything helpful yet.

I read that the floating-point based ALU is capable of 25.6 GFLOPS but can't find anything on an integer-based ALU...

One of my coworkers asked me this Friday afternoon and it has been driving me crazy ever since!
 

Matthias99

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Oct 7, 2003
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From http://www.blachford.info/computer/Cell/Cell1_v2.html

Each Cell contains 8 SPEs.

An SPE is a self contained vector processor which acts as an independent processor. They each contain 128 x 128 bit registers, there are also 4 (single precision) floating point units capable of 32 GigaFLOPS* and 4 Integer units capable of 32 GOPS (Billions of integer Operations per Second) at 4GHz. The SPEs also include a small 256 Kilobyte local store instead of a cache. According to IBM a single SPE (which is just 15 square millimetres and consumes less than 5 Watts at 4GHz) can perform as well as a top end (single core) desktop CPU given the right task.

*This is counting Multiply-Adds which count as 2 instructions, hence 4GHz x 4 x 2 = 32 GFLOPS.

32 X 8 SPEs = 256 GFLOPS

I'm not sure how you spent five hours on this... that page was the first Google hit on 'cell processor architecture'.