Posted this on a different thread & thought in the interest of helping others who come searching for information later I'd cross-post this here so it'd be easier to find for people in a similar situation...
Regarding the Sil0680a controller cards and NEC drives here is a true story that will make you go "Hmmmm...."
I have a Dell XPS system (very nice system except a little too pricy unless you get a 30% discount code like I did & throw some Klipsch 5.1 Ultras in the basket for 30% off of those, too with free shipping) and one of the features was it had one of the newer Intel chipset-based motherboards with just one PATA controller. Plenty for most people.....unless you are a cough CD Freak cough that has 3 (Three!!!) PATA optical drives.
One of these drives is a NEC ND-3500AG drive & after trying everything in the world and every option available to me if I wanted my drives to be set up the way I wanted them I was going to need to hook my NEC drive to a Sil0680a card. As an aside, the Belkin RAID version of this card is the cheapest of all the brand name cards & you get a good warranty.
I had the same DMA problem listed in the thread referenced above. I tried everything. I flashed different versions of firmware of both the RAID & non-RAID variety to the controller card. I flashed different firmware revisions to the NEC drive. I tried different cables...I even tried an 80-pin cable out of desperation. Nothing worked.
After the frustration and depression passed I took stock of the situation. I was not getting the full potential out of this DVD burner, but what was I missing? Really the only thing I couldn't do with things the way they were was burn at 16x. Well, to be honest, that's no loss at all to me because near 100% of the media I buy is 8x rated media & I only burn at 8x so that consoled me a bit. I just let things ride the way they were. After all, no use banging your head to attain a feature you never use, yes?
Now here's where things get interesting...fast forward five or six months & I am having a Burning Day. I'm consolidating stuff, sorting, burning, and deleting...doing some cleaning out of the old hard drives and making some archival backups. I'm surfing around the net while I do this...that's how I do things. Catch up on my 'net reading & I'm able to be right there when the drives spits out the burned discs.
Anyway, I spy new drivers for my motherboards on-board Gigabit NIC (Broadcom BCM57xx-based in case you were curious). Being the upgrade whore that I am I stop what I'm doing, let the current disc finish burning, and upgrade the NIC driver. My old driver version was v7.xx and the new and improved version was v8.xx so I'm thinking maybe big changes were afoot & I rebooted the PC even though I didn't have to just to make sure things would work properly.
I got back to my desktop & went back to burning DVDs and such. Now before DVD Decrypter would always default to 8x burning speed as that was the max my drive would support connected to the Sil0680a. Well, this time it defaulted to 16x! I checked all the usual places in Windows & with the Sil0680a drive utility thing and every place I looked now stated the drive was running at its max rated speed and data transfer rates. It has operated from that day to this day at maximum performance.
All that from just changing a NIC driver and rebooting. Weird. Like I said, makes you go "Hmmmm...."
P.S. Sorry this is such a long post, but I wanted to outline the course of events and stress that it truly was only a driver change for a seemingly unrelated piece of hardware that was responsible for the increase in functionality and performance.