Seagate Momentus XT 750GB hybrid hard drive

The original Seagate Momentus XT impressed us in 2010 with its innovative cache of SLC NAND flash memory: a small 4GB chip that stored a copy of commonly-accessed data and delivered it when needed at speeds much, much faster than the hard drive’s spinning platter could muster. While the rest of the Momentus XT functioned at similar speeds to any other fast laptop hard drive, this crucial flash memory did amazing things like reduce boot times and program loading times to rival the fastest solid-state disks. The new 750GB version of the Momentus XT doubles the size of the flash memory and adds a series of new algorithms to improve boot speed, as well as including another 18 months’ improvements in traditional laptop hard drive technology.

• Read our review of the original Momentus XT
• SSD prices will fall below $1 per GB in 2012, says IDC

Seagate Momentus XT: Design and specifications

The Seagate Momentus XT design is a 2.5in model, designed to be used primarily in laptops — there’s no hybrid drive option for desktop PCs but the Seagate Barracuda XT is as close as they come. As it fits the standard laptop drive dimensions, the Momentus XT measures 9.7mm x 70.1mm x 100.6mm and weighs 115g — only 5g more than the Momentus XT 500GB it dethrones as Seagate’s laptop performance king. It has, as you’d expect, a standard SATA and power connector layout.

The 750GB Seagate Momentus XT is a 7200rpm model, and supports the SATA III standard of 6Gb/s throughput. It has a 32MB disk cache on top of its 8GB SLC NAND flash, with a quoted average latency of 4.20ms and random read and write seek times of 11.0ms and 13.0ms respectively. Its power consumption is up from the 500GB model’s 0.8W idle and 1.1W operating to 1.2W and 2.4W, with a rise in drawn amperage from 0.58 A to 0.70 A.

Seagate Momentus XT: Performance and features

The Momentus XT shines as a system drive, loaded with either Windows 7 or Mac OS X Lion. It’s no surprise that Dell, Asus, Sony, Toshiba and Alienware are using Seagate Momentus XT drives in some of their laptops — the performance advantage conferred by the onboard flash is very noticeable in real-world testing.

We loaded the Momentus XT 750GB with Windows 7 Service Pack 1 for the majority of our testing, installing it from scratch on a fresh drive. We did the same with last year’s Momentus XT 500GB, as well as an 80GB Intel X25-M and a regular ol’ Hitachi Deskstar 7K1000.D . Our test system was an Intel Core i7-2600, 8GB of DDR3 RAM, and an AMD Radeon HD 6970 on a Intel reference P67 motherboard.

We measured boot-up times from the second we hit the power button to the time Windows 7 finished automatically loading the Firefox browser on our test system. Intel’s SSD was the speed queen, measuring 12.1 seconds with very little difference between the first run and any subsequent runs. Both Seagate Momentus XT hard drives returned identical performances of 15.2 seconds, but there was an important difference: the older 500GB drive took six runs to reach its fastest time, but the 750GB version was as fast as possible from the second run onwards. The traditional Hitachi drive took an unimpressive 42.1 seconds.

A more intensive boot run exposed the difference between the two drives. We queued up Adobe Photoshop Lightroom, Photoshop CS 5.5, Microsoft Word, Excel and Firefox to run after a fresh Windows boot, and the results were impressive. While the Intel X-25M still beat out the crowd with an overall time of 20.6 seconds, the Momentus XT 750GB (after three runs) edged out the 500GB (also after three runs) by two whole seconds: 22.3 seconds versus 24.5 seconds. The Hitachi Deskstar 7K1000.D was comparatively glacial at 1min 12.3 seconds.

What’s evident from the boot and program-loading tests is the close margin between the Momentus XT drives and the Intel SSD. Synthetic results do the most to display the difference between the individual Momentus drives, though — we used CrystalDiskMark and HD Tune Pro to catalog each drive’s performance.

We didn’t see any significant difference in outright disk transfer rates after multiple runs — and so we shouldn’t. The 750GB Momentus XT edged out its predecessor in HD Tune Pro with transfer rates at a minimum of 57.9MB/s, a maximum of 123.3MB/s and an average of 94.9MB/s, where the original 500GB model was only able to muster 54.1MB/s minimum, 107.0MB/s maximum and 86.2MB/s average. This is a noticeable difference in average speeds, which manifests itself in real-world testing as well: the 750GB took 27.0 seconds to write a single 2.84GB file to disk, where the 500GB took 29.1 seconds. The burst rates of the 500GB and 750GB drives respectively were 170.6MB/s and 198.6MB/s.

What was interesting was the effect of the disk cache upon access time reporting in HD Tune Pro. Where the Seagate Momentus XT 500GB took 17.6ms in the test the first time, it was down to 0.3ms after three runs. The 750GB took 15.5ms the first time and 0.2ms from the second run onwards. This represents the disks’ learning capability working at its best.

Seagate Momentus XT: Conclusion

Seagate’s approach to bringing SSD-like performance to its hybrid drives has paid off, with bigger dividends in this iteration versus the last. While the Momentus XT 750GB’s cost per gigabyte is clearly ahead of SSDs, it is one of the most expensive laptop hard drives you can buy: we’ve seen it for around the $329 price point, versus around $239 for a regular Seagate Momentus 750GB drive, or $215 for the older 500GB Momentus XT. We still think it hits a good compromise between price and performance, though.