Slow transfer speed and after reboot fast?

When I want to transfer dvd media on my nec3550a@4551a drive to hard disk it sometimes start transfer at lower speeds 2.5 MB/s and transfer is very slow.When I reboot my pc and start transfering from same dvd again my start speed is 8.5 MB/s and the transfer is very fast-whole dvd 4.7 disk is transfered for about 5 minutes.

And that is very often.

Does anybody know why?

Check if DMA is enabled. Maybe this is your problem

DMA is always enabled.When I have slow transfer rate I have no problem to burn dvd disc even on 16X speed.It is only issue when I read disc till I reboot.

I can’t figure what can be.

What IDE drivers do you have?

My mobo is MSI KT4AV with via kt400a chipset and instaled via 4in1 drivers.
I have no problems in transfer with my dvd rom and liteon 52327S only with nec
till reboot.