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.

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  • jpkang - Wednesday, July 15, 2009 - link

    There are a few reports on Twitter (">, but some right after WWDC that are not currently appearing in search results) that Snow Leopard has dramatically increased battery life. I'm curious to see how much of an impact it will have on real-life battery results (let alone marketing claims) come September.
  • Eventide - Monday, July 6, 2009 - link

    Windows 7 should be better in terms of Battery Performance actually. They rewrote the kernel and scheduler for Windows 7 to let the CPU reach deeper sleep states which was impossible due to interrupts occurring every 8 ms or so.
    Could you try to bench Win7 with some more going on like watching DVD? According to MS it should perform better then. Also Vista SP2 may behave differently from SP1 in terms of battery performance.
  • blufire - Monday, June 22, 2009 - link

    ...addresses the SATA issue.">
  • purezerg - Sunday, June 21, 2009 - link

    hmm. I installed OSX on my laptop and OSX was 3hrs when it's 8hrs with vista.
  • Deusfaux - Thursday, June 18, 2009 - link

    ...instead of their advertised 3.0gbps.

    Can you look into or at least call THEM out on that too, Anand?

    I've been shopping for a HDD dock for a long time now, and it's only taken this long because nobody can seem to provide one with eSATA that runs at 3.0gbps.
  • majortom1981 - Wednesday, June 17, 2009 - link

    I am thinking that its a drivers issue on using windows on a mac and battery life.

    Do you honestly expect apple to let windows on their hardware get better batterylife then osx?

    I would think its a drivers issue and not how the OS is programmed.

    My laptop automatically underclocks itself, dims the screen and other things under vista and windows 7. Does windows 7 do these things on a mac pro?
  • TEAMSWITCHER - Wednesday, June 17, 2009 - link

    He tested a Lenovo X300 which is similar to the Mac Book Air and got similar results in Vista. So Lenovo must have some pretty bad drivers as well.
  • SoCalBoomer - Wednesday, June 17, 2009 - link

    Win7 would do that only if Apple set up its drivers to do that. . .

    Which I sincerely doubt they would do - Apple has no incentive to make a competitor's operating system perform well on their hardware. They want people to switch.
  • dolcolax - Tuesday, June 16, 2009 - link

    i was just wondering if the tests for windows was done by booting on windows, or by using VMware fusion or parallels? if you're just emulating windows, will that have an effect on battery life?

    so it seems that by using windows, you'll have a higher power consumption? so is it safe to say, that the mac mini which was advertised to idle at 13W will have an increase in power consumption while running windows?
  • gourygabriev - Tuesday, June 16, 2009 - link

    I think the reason why Mac OSX is fairing better in battery life is because the way it uses its resources. I am using a my Macbook right now Aand I noticed that if I open 10 browsers, Only the browser that is currently on the top screen is getting worked on. anything that I've minimized will be left alone, so less cpu cycles are being used. I know this for a fact because if I upload pictures on flickr and i minimize the browser it doesn't upload till the screen is on. Just the workload i guess. Windows always have something running in the background while OSX seems to halt programs I've noticed. Mind you I'm not a techie so I am not qualified to assess anything. This is just something I've noticed when using my stuff.

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