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If I buy a 1TB hard drive with a SATA 3 Gb/s interface, will my computer be able to use it with it's 1.5 Gb/s SATA interface?

• Laptop hard drive filter: I'm in the market for a new hard drive for my laptop, and I want to get the best one my computer can handle. My computer seems to have a 1.5 Gb/s SATA interface; will it be able to handle a 3 Gb/s SATA interface hard drive? A quick question for all you computer hardware junkies out there who'll know more about this kind of stuff than I do: the laptop I currently have is a few years old, and has a hard drive that is no longer large enough for my needs. I'd like to upgrade the hard drive, but I don't know which interface type to get so that the hard drive I buy works with my computer. I've always had good experiences with Western Digital hard drives, so I've decided to buy one out of their Scorpio Blue line. When I looked at their website, I noticed that the site says that they offer these hard drives in a number of different capacities; the capacity that I'm interested in is the 1TB capacity. They also offer these hard drives in 3 different interface types: SATA 3 Gb/s, SATA 1.5 Gb/s, and PATA. Now, I own a MacBook running OS X 10.5.8, and I'm somewhat computer literate, so I checked System Profiler to see what interface type my computer has. Under Hardware > Serial-ATA, it says that I've got something called a "Intel ICH8-M AHCI", which has a speed of 1.5 Gigabytes. So far so good. However, on the Western Digital website, it seems that the hard drives they sell under the SATA 1.5 Gb/s interface only go up to 320 Gb. However, Western Digital does sell 1TB hard drives with the SATA 3 Gb/s interface. Thus, my question ultimately becomes: if I buy the 1TB hard drive with the SATA 3 Gb/s interface, will my computer be able to use it (even if it can only write and read to it at a speed of 1.5 Gb/s)? Thanks in advance, guys and gals. Be sure to stay tuned for the follow-up question that's undoubtedly sure to follow, where I ask how to format/set up/install operating system on said hard drive.

• Answer:

  It will be fine. A 3Gb/s device will autonegotiate down to 1.5Gb if that's what the controller speaks. There were some problems with very old 1.5 Gb/s controllers being unable to do this autonegotiation, so drives have a jumper to force 1.5 mode if necessary. But your chipset isn't one of them so it really doesn't matter. And just to be pedantic: it's 1.5/3.0 gigabits per second, not bytes. And since these interfaces use 10-bit encoding for each 8 bit byte, that means the effective rates are 150 and 300 megabytes per second. On top of that, today's fastest 7200 RPM drives cannot sustain 150 megabytes per second (they're at about 130), and a 2.5" drive at 5400 RPM like the one you're talking about will not even come close. So the 1.5/3.0 distinction in your case is entirely academic and irrelevant.