2009/8/11 Ian Murray murrayie@yahoo.co.uk:
In my haste for help, I stupidly hit reply and changed the subject which I thought was enough for a new message, not giving much thought for the threading, etc. So apologies for the hijack, although I would think it fairly obvious that it wasn't deliberate or obvious to me... or a big deal really. My mail doesn't thread.
Some further info for those actually interested in helping, I forgot that the HD in question had an Ubuntu 8.10 install on it, so I fired that up and hdparm -t produced 56MB/Sec. So the issue is either kernel or config.
Check if ultradma and unmasq interrupts flags are set(both under ubuntu and centos):
hdparm -u -d /dev/hda