HD Tach
We tested HD Tach with the benchmark's full variable zone size setting.

HD Tach's straight-line sustained transfer rate tests expose the Caviar Green's slower spindle speed, pushing it well behind the 1.5TB Barracuda and most of the 7,200-RPM field. The gaps between the 250GB/platter Caviar GP, the 333GB/platter Caviar Green 1TB, and the latest 2TB model are particularly interesting. Moving from the four-platter Caviar GP to the three-platter Caviar Green represents a 33% jump in per-platter capacity and about a 30% increase in sustained throughput. However, the jump from the three-platter Caviar Green 1TB to the four-platter 2TB model represents a 50% increase in per-platter capacity but not even a 4% improvement in sustained transfer rate.

Burst speeds are independent of platter counts and densities, so it's no surprise to see the 2TB Caviar Green near the front of the pack here.

However, a slower spindle speed does tank the drive's random access time, which is among the slowest of the lot, and roughly equivalent to that of the 1.5TB Barracuda. Both four-platter GreenPower drives have relatively high random access times, but the three-platter Caviar Green is a good millisecond or more quicker.

HD Tach's margin of error in the CPU utilization test is +/- 2%, which neatly covers the range of drives we're looking at today.