IOMeter
IOMeter presents a good test case for both seek times and command queuing.

The Barracuda XT gets absolutely worked in IOMeter, delivering much lower transaction rates right out of the gate. The XT's performance scales relatively poorly as the load increases, too.

So much for the SATA 6Gbps standard's improved command queuing, at least as it's implemented in the Marvell controller. When connected to the Marvell, both drives hit a performance wall at 32 concurrent I/O requests, which just happens to be the depth of the Native Command, er, Queue. The P55's performance continues to scale right up to 256 outstanding I/O requests.

At least the Marvell controller doesn't consume more CPU cycles than the Intel one. Then again, these configs are barely registering on the CPU utilization scale with our eight-thread Core i7.