Speed problems with plextor NEED HELP



First this is my hardware;

Scsi card adaptec 19160 (ultra 160)
Scsi cd rom plextor PX 40TS
Scsis cdr plextor PX-W 124TS
Scsi hd IBM ddys T09170N
Win 2000

The problems are , with drive test benchmark programs i only get 10x througput with px 40 ts.

And when i try to burn 12x it will nott work , it works up to 8x but thats it! (i have tried to burn both from HD and cd-rom same result) burn program always says “buffer underun”? is my cd rom to slow or is my burner defect?
Need help quick!
(please answer to my email if you have any ideas)

Thank you



Did you check termination is only present at one device and that should be the last one?