In article <35898892.6090336@mail.danbbs.dk>,
	dinsen@danbbs.dk (Anders Dinsen) writes:
> dd if=/dev/sd0d of=/dev/null

You should use the raw device...

> But when I did the same on /dev/wd0d, I got a figure which was about
> three times less!

... and a decent block size in both cases. Try e.g. this

dd if=/dev/rsd0d of=/dev/null bs=1024k
dd if=/dev/rwd0d of=/dev/null bs=1024k

-- 
Matthias Scheler                                http://home.owl.de/~tron/