It's the P6 now

The present generation of supercomputers has been using custombuilt processors which are very difficult to maintain. Now, if the
Accelerated Strate~c Computing
lnitiative, a US department of
energy-funded project is successful,
this may become a thing of the past.

The project envisages building a
massive computer using high performance microprocessors of the
kind used in personal computers.
The machine will do 1.8 trillion
mathematical operations in a second, an improvement of 10 times
over existing machines. The basic
processor used will be P6, the next
generation processor after the
Pentium.