9.5 Versus 12.5 mm: Which Notebook HDD Is Right For You?
Notebook drive manufacturers can choose between two drive heights: 9.5 mm and 12.5 mm. At 9.5 mm, most drives are limited to two spinning platters, while 12.5 mm has enough room for three, enabling higher capacity. We compare the two 2.5" variants.
9.5 mm: MK6465GSX, 640GB
We picked two Toshiba hard drives for an apples-to-apples comparison. The first product is the MK6465GSX, today's 640GB drive. There is also a 750GB model. We haven't received this drive yet, but differences compared with the 640GB should be minor.
The 640GB model uses two platters and stands just under a 9.5 mm height. The spindle speed is 5,400 RPM, the standard rotation rate for mainstream and high-capacity laptop drives. Toshiba specifies a MTBF rating of 600,000 hours, but it's hard to compare this because Seagate and WD do not publish any reliability specifications. Toshiba's 3 Gb/s SATA interface and 8MB cache are check box items, as is the operating temperature of 5°C to 55°C. A few drives can run at up to 60°C, but this shouldn't be relevant in most environments. Toshiba also offers models at 160, 250, 320, and 500GB capacities.
We measured a maximum read transfer rate of 91 MB/s. That’s excellent for a conventional hard drive, and although the three-platter unit delivers a bit more throughput, this two-platter model wins on access time and application performance. Amazingly, both drives show almost identical idle power consumption and maximum read speeds.
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