UDMA 66 support?

When I read the review of the Plextor 716 here at cdfreaks I noticed that the drive support Ultra DMA mode 4 (perhaps other drives do this too?), but is this increase in bus speed compared to UDMA 33 needed? The maximum tranfer rate of a 16x dvd-burner is no more than 22MB or so, right? So in what situations will you benefit from mode 4?

(The reason I’m asking is because I’ve got an old computer with an UDMA 33 controller and I’ve been thinking of getting a controller card to get more out of my three 120GB Seagate Barracud 7200.7 and that way get a free channel for a burner on the on-board controller. I was thinking of choosing a Promise Ultra ATA/133 TX2 because it’s cheap and easy to find where I live. I did read the thread here where alot of people said Promise wasn’t recommended for optical drives so I figure I’d use it only for hard drives.)

One situation where I have seen a benefit is when a UDMA-66 DVD burner is put in an external USB2 eclosure. In this case I have been able to easily get 16x burns.

Another case, is if you have no alternative than to share IDE ports between drives…

22Mb/s is 2/3 of ATA/33, so even though timings can be split, 2/3 of the time (and throughput) are already used, and at ATA/66 - another drive is left with only 1/3 of it (22Mb/s).

If you MUST share a cable between drives, the situation improves if they are both ATA/66 or better, though if you can avoid transfer involving both drives on one cable, so much the better.

I’m guessing that ATA/66 for a writer, may help to hold together a setup that would have been a non-starter in the days before burnproof, and that “old hands” would still frown on today.

A transition to native S-ATA II would solve many problems at once but even the computer companies are very conservative. Still eggs and hens.