毎サイクル64bit計算できるそうだが

ttp://developer.intel.com/technology/itj/q12001/pdf/art_2.pdf
Intel Technology Journal Q1, 2001
The Microarchitecture of the Pentiumﾆﾊ 4 Processor
p.10より引用

In the Pentium 4 processor,the FP adder can execute one
Extended-Precision (EP) addition, one Double-Precision(DP)
addition, or two Single-Precision (SP) additions
every clock cycle.

(中略)

The FP multiplier can execute either one EP multiply every two
clocks, or it can execute one DP multiply or two SP multiplies
every clock.