Xeon as a worthwhile platform?

[Torbjorn Granlund]

Carl Devore <devore@math.udel.edu> writes:

  On 11 Apr 2003, Torbjorn Granlund wrote:
  > Consider multiplying two 512-bit numbers.  A 32-bit processor
  > will need (512/32)^2 = 256 32-bit multiply instructions to form
  > the product.  A 64-bit processor will need just (512/64)^2 = 64
  > 64-bit multiply instructions.
  
  At what length do faster-than-O(n^2) multiples kick in?
  
For the Opteron with the yet-to-be-written assembly code?
My tea leaves haven't told me that.

(I have seen cutoff points of between 8 and 70 for other
microprocessors.  The unit is "limbs" here.)

-- 
Torbjörn