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To: jcholewa who wrote (21688)12/6/2000 4:04:08 PM
From: dale_laroyRead Replies (1) | Respond to of 275872
 
Keeping the fp pipelines of the x87 flowing seems to take a minimum of one FXCH/FLD/FSTORE for every two calculations. While the Athlon is fully capable of executing this many FXCH/FLD/FSTORE operations without any performance hit due to its free FXCH and separate FLD/FSTORE pipe, decode becomes a real problem. Thus the peak sustainable x87 fp execution rate is four calculations every three cycles, versus less than four calculations every four cycles for P4 using scalar SSE2. The Athlon can exceed the per cycle fp performance of P4 by more than 33%, but nowhere near 2x.