RSA accellerators on ISA/PCI cards?

[Simon Spero]

Does anybody have any recommendations for a good RSA accellerator 
available on an ISA/PCI card? I'm looking for something that can be used 
with numerous public/private keys, though the ability to have one 
tamperproof key would be a bonus.

Thanks
Simon
----
(defun modexpt (x y n)  "computes (x^y) mod n"
  (cond ((= y 0) 1) 	((= y 1) (mod x n))
	((evenp y) (mod (expt (modexpt x (/ y 2) n) 2) n))
	(t (mod (* x (modexpt x (1- y) n)) n))))