This evening I was ripping 2 dual layer DVD videos to hard drive.
I noticed that my NEC 4571A copied the whole disk, about 7.5gb, to hard drive in about 12 minutes, with an average speed of around 10x. it peaked around 12x.
My other drive, an NEC 2510A, took more than twice as long on a disk almost the exact same size - almost half an hour, and its average speed was about 3.5x. it peaked around 4x

The 4571A is my primary master. The 2510A is my secondary master.
I have 2 x 250gb WD SATAII 16mb cache hard drives. The DVD drives were ripping the DVDs to the same hard drive, my second drive that I use for storage.
I tried deleting the ripped files, swapping the disks over, and trying again, just in case it was a problem with the DVD disks. The same thing happened - the 2510A lagged behind.

So I came online to do some reading. I read about 'rip lock' and how it can be removed by flashing new firmware. I checked the firmware of my 2510A, it was version 2.8. So I downloaded a version of 2.8 with rip lock removed and RPC1. Flashed it. While I was at it, I thought I would do the same with my 4571A - it had firmware version 1.01, so I got a v1.01 with RPC1. Flashed it. Restarted my PC.

Tested the 2510A - it's made no difference. Still rips very slow. Starts off around 2x, crawls up to 3-4x. Oh well, nothing ventured nothing gained.

Then - to my horror I discover my 4571A is no longer running as fast. It, too, is starting around 2x, crawling up to 3-4x. What happened?!
I thought - good job I backed up the original firmware! So I flashed back to that. No luck - still rips slow!

What's the problem here? What can I do?