Disk I/O performance
Here we get to see whether Native Command Queuing has any measurable benefits. I used Iometer with both workstation and database access patterns to simulate real-world disk loads. Note that there are two sets of results for the 925X. One of them is without Native Command Queuing, using the built-in Microsoft disk driver in WinXP. The other uses Intel's Application Accelerator for RAID 4.0 driver, which enables Native Command Queuing support—and not surprisingly, that's the result labeled "NCQ" in the graphs.

In all cases, we're using Maxtor's MaXLine III SATA 150 drive that features a 16MB buffer. This is a pre-production drive with NCQ support.

Without NCQ, the 925X chipset is very closely comparable to the 875P and K8T800 Pro chipsets. But with both access patterns, Native Command Queuing shows higher transaction rates, lower response times, and only negligible spikes in CPU utilization (below about 3%) versus the non-NCQ configs.

Here is a feature that folks should be lining up for. Hard drives are the slowest components in a modern PC, and the 925X with Native Command Queuing delivers SCSI-like performance in a Serial ATA drive. We'll have to test RAID with NCQ soon.