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Technology Stocks : Advanced Micro Devices - Moderated (AMD)

AMD 217.53

+1.5%

Nov 28 9:30 AM EST

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To: Tenchusatsu who wrote (17595)	11/3/2000 10:29:36 PM
From: minnow68	Read Replies (1) of 275872

Tenchusatsu, You wrote "can you show me a heavy-duty application which crunches the FPU but not bandwidth?" Yes. An example is multiple linear regression. The problem is related to the square of the number of variables involved. Therefore, if you are performing a regression with less than 178 variables (very few problems use that many), then the entire accumulation array can be held in a 256K L2 cache. This means that for a regression of 178 variables, one would have to perform about 64K floating point ops for each 1424 bytes of memory read. Another way to look at this is the flops/(bytes of bandwidth) ratio is about 45. This problem is of extreme practical interest. Regression is used extensively in many fields. Similarly, there are other mathematical problems were complexity expands even faster. For example, flops needed in regression is proportional to the square of the number of variables. There are problems where calculation time scales to the cube or worse. For these problems, the bandwidth does not help much as long as the working set fits in cache. Mike

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