The SATA 3Gbps vs. 1.5Gbps Issue

All unibody MacBook/MacBook Pros use NVIDIA’s GeForce 9400M chipset. The chipset includes native support for up to six SATA ports running at 3.0Gbps (300MB/s max transfer rate). Here’s a copy of OS X’s system profiler showing 3.0Gbps as the interface speed on the previous generation MacBook Pro:

3 Gigabit...only on the first unibody MacBook Pro

Unfortunately, the current version of the MacBook Pro appears to only support 1.5Gbps SATA. I’m not sure whether this is an OS, drive or hardware problem, but your drive is limited to transfer rates of 150MB/s. For most laptop drives, this isn’t a problem. Your 5400RPM SATA drive just isn’t going to be moving anything at 150MB/s. The real problem lies with high performance SSDs.

Let’s look at the read/write performance of the three top SSDs on the market today: the Intel X25-M, the OCZ Vertex and the Corsair P256:

New 15-inch MacBook Pro (73WHr battery) 4KB Random Read 4KB Random Write 2MB Sequential Read 2MB Sequential Write
Intel X25-M 54.2 MB/s 22.2 MB/s 230 MB/s 71 MB/s
OCZ Vertex (Indilinx) 34.9 MB/s 6.55 MB/s 256 MB/s 137 MB/s
Corsair P256 (Samsung) 29.1 MB/s 0.78 MB/s 207 MB/s 178 MB/s


You’ll see four categories of performance: random read, random write, sequential read and sequential write speed. All four categories matter to the performance of your hard drive but some are more noticeable than others depending on what you do.

Random read/write performance actually contributes to your system feeling fast more than anything else. These are the sorts of transactions that happen when you’re launching applications or searching for files. Sequential read/write transactions happen when you’re copying large files to/from your drive. The latter is less common than the former for most users but that’s why you don’t see the 1.5Gbps issue really impacting real world performance on the new MacBook Pro.

All three of the SSDs in the table above would be interface limited on the new MBP because of their high sequential read speeds. If you were copying large files from the SSD in your MacBook to a similarly fast device, the transfers could take longer. I doubt the performance difference would be significant or noticeable in real world notebook usage, but it doesn’t change that there’s no reason to take a step backwards like that. In the coming years we’ll see more drives that can consistently break 150MB/s; Apple artificially limiting performance today would just hinder progress.

I’m not sure what the issue is since the 9400M does support 3Gbps SATA. Perhaps it could be one of the mystery optimizations Apple did to increase battery life well beyond reasonable expectations? Or perhaps it’s just an issue with the firmware and something that will be corrected in the near future. It's worth noting that the version of OS X 10.5.7 that ships with the new MacBook Pro is a different build than the one everyone else gets to download.

It’s something to keep an eye on and I’ve already sent out some probes trying to gather more on the issue.



View All Comments

  • mitocho - Monday, June 15, 2009 - link

    Have you though about wiring the new MBP battery to the old MBP? I'd like to see just how much of a difference the battery makes. Seems like the new MBP has some extra optimizations. Reply
  • winterspan - Wednesday, June 24, 2009 - link

    Just wanted to mention that Apple has already issued a firmware update that has corrected the SATA problem and enabled SATA/3.0Gbps functionality on all new MB Pros... Reply
  • Intelman07 - Monday, June 15, 2009 - link

    Did you get the optional 9400M + 9600M GT? I think Windows will run the discrete 9600M GT instead of the 9400M integrated card. Reply
  • Anand Lal Shimpi - Monday, June 15, 2009 - link

    This is the base $1699 model, there's no 9600M unfortunately. The results echo what I've seen in the past with OS X vs. Vista, it's just nice to have an update. Hopefully we can get a real response from Microsoft this time.

    Take care,
  • sprockkets - Monday, June 22, 2009 - link

    Take a look at what the .7 update to 10.5 is doing for these Mac people.">
  • Intelman07 - Monday, June 15, 2009 - link

    Wow, that is a shame. I was looking at purchasing one of these (first saving) for school. It would be nice to go ~7 hours without a charger on campus. I suspect most of the tools I use are Windows only though (I am almost certain).

    There is a real lack of good Windows PCs in the market. Nothing with battery life near as good, or a body construction out of one nice block of metal. My piece of crap Dell Inspiron 1520 is literally falling apart at this point. I have had 5 repairs on it. I suffered from the faulty 8600M GT, then my motherboard went bad, then my ram went bad, then my LCD flickered, now my casing is getting small cracks....

    What is one to do!?! I might just settle for lab computers at this point :( It would be cheaper.
  • teohhanhui - Tuesday, June 16, 2009 - link

    Isn't Inspiron in a totally different price range? Reply
  • Intelman07 - Tuesday, June 16, 2009 - link

    I paid ~1800 for my Inspiron. That is pretty much in line with the MBP. It was one of the first to have the Santa Rosa chipset.

    And yes, I would think that Apple Macbook Pros are higher quality, since they use a metal casing and not plastic. Plus innovative battery technologies. I have never owned one though, I could be wrong. They feel nice in the store.
  • Pirks - Tuesday, June 16, 2009 - link

    Are you saying that Macs are more expensive because of higher quality, and not because of the shiny logo? Reply
  • Fallen Kell - Monday, June 15, 2009 - link

    I know that on my 17" Unibody Pro Vista uses the 9600M which does chew up the battery life. Vista support isn't really that great... It took me about a week to get it really stable and even then I still have to attach a mouse to get right clicks to work properly. I didn't think the power usage was just due to the OS, but mainly from the use of the 9600M. Looks like there is even more of a battery tax for using Vista (I currently mostly use OS X, but eventually might do more). Reply

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