The new Momentus is still available with both commonly used interfaces: UltraATA/100 and Serial ATA I (SATA), which runs at 150 Mbps. It is true that UltraATA is now rather long in the tooth as an interface standard, but its efficiency is still adequate for the fastest desktop hard disks. It is definitely adequate for notebooks, where the 85 Mbps practical speed of UltraATA/100 is well above the maximum of 50 Mbps reached by notebook drives.

The SATA versions of the Momentus drive are compatible with Native Command Queuing (NCQ), as is usually the case with Seagate. NCQ requires support from the controller, drive and drivers, and makes it possible for the commands coming into the drive to be sorted so that they can be processed in the most efficient order. The aim here is to keep the repositioning of the read/write heads to a new track as infrequent and short as possible.

The ST9120821AS is equipped with 8 MB of buffer memory and a modern spindle motor with liquid bearings, which runs very quietly. Seagate gives the average seek time to be 12.5 ms. The general access time of 16.7 that we recorded confirms this value (access time includes seek time and spindle latency.)

The I/O performance achieved by Momentus 5400.2 120 GB was considerably higher than that of its predecessor with 100 GB. However, the command queuing of the SATA version was notable because the UltraATA/100 version is somewhat slower. This benchmark is important if you work with many applications or numerous file operations. Irrespective of this, the transfer performance of both models is good, at up to 40 Mbps.