Seagate seems to have another class of hard drives that isn't Barracuda. Link is
here
They just call is Internal 3.5-inch Hard Drives. From there you see the 500GB drives.
From there you will see a 500GB PATA drive with just 8MB of cache.
Link here
Now I know the deal is pointing out a SATA drive put I am just putting information out there so people can see there are large drives out there with 8MB cache instead of 16 MB cache. I can't find a 500GB SATA with 8MB cache on Seagates website but there are 7200.10's made with 8MB cache. Links below.
The TD spec might be wrong, although anything is possible because the 7200.10 made two versions of the 320 GB SATA drive, one with 8MB cache and another with 16MB cache. Link below from the Seagate website.
320GB 7200.10 SATA with 8MB cache
Seagate ST3320820AS
320GB 7200.10 SATA with 16MB cache
Seagate ST3320620AS