Are SATA 3Gb/s and 1.5Gb/s hard drives interchangeable?

July 5, 2011 3:05 PM

My computer (Macbook pro 4,1) has a Serial ATA (1.5Gb/s) bus. Can it use a hard drive that has a speed of 3gb/s?

I have this computer.

It currently uses this (PDF) hard drive (model no: Hitachi HTS542525K9SA00)

I'm going to upgrade to a 500GB hard drive, but I'm confused about what SATA speed I need to be going for. Could it be 3 Gb/s, or should I stick with 1.5 Gb/s

Thanks!

posted by radiocontrolled to computers & internet (4 answers total)

Yes, SATA maintains backward-compatibility (in both directions, refreshingly enough). With two caveats:

You can't hotplug it, and you can't (easily) have more than 2TB.
posted by pla at 3:15 PM on July 5, 2011

Just a followup - It hit me a minute ago that you mentioned this as a Macbook. You can electrically connect any SATA drive, but make sure you can physically fit your new drive in the case before buying. 2.5" drives come in a variety of thicknesses, and you can even get 1.8" drives (though fairly uncommon).

A quick Google search suggests the Macbook Pro will accommodate even the largest of the 2.5" drives, but, caveat emptor.
posted by pla at 3:31 PM on July 5, 2011

A 5400 RPM 2.5" drive can't come anywhere close to saturating a 150 MByte/s link (which is what the 1.5 Gbit/s link equals after overhead) -- you'd be very lucky to get half of that. So the issue is moot for all practical purposes. Sure, they make them with the 3.0 interface, but that's really just because that's what the current chipsets are capable of. You're going to be limited by the rotational rate times the areal density, not the speed of the interface.
posted by Rhomboid at 3:43 PM on July 5, 2011 [1 favorite]

Rotational rate and areal density limits don't apply to data held in the drive's internal cache. You could, in theory, briefly saturate the link with cached data, so there might, in theory, be a usage pattern where you'd actually see a 3Gbit/s interface increase throughput.

I doubt you'd ever notice in general use, though.

If you want serious speed from a 2.5" SATA hard drive, get a 7200RPM 1TB model and short-stroke it. If you leave the second half of a 1TB drive as unpartitioned free space, all your data will go on the outer half of the available platter area, which translates to about 40% of the available platter radius; seeks will be shorter, and sequential transfers will benefit from higher angular density.
posted by flabdablet at 2:23 AM on July 6, 2011