The computer has 2Gb of memory, so I just repeated the dd with the
aforementioned Fedora and got:

  % time dd if=/dev/sda of=/dev/null bs=1024k count=4096
  4096+0 records in 
  4096+0 records out

  real    0m49.366s
  user    0m0.015s
  sys 0m6.148s

So a rough and ready estimate is 4096/49.366 = 83 MB/s >> 4 MB/s
(so I don't think I will repeat with 4GB under NetBSD..)

Are any of you using mpt(4) successfully? If so with what hardware?
(It would make playing "spot the difference" easier..)

Cheers,

Patrick