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

  • bspeck1 - Tuesday, June 16, 2009 - link

    If patterns repeat themselves Anand, shouldn't we expect a big update on the MacBook Pro in October? In your recommendation should I wait to buy until October for a faster Intel chip or is this Summer update stellar?? Reply
  • sadffffff - Tuesday, June 16, 2009 - link

    I would take a pc laptop, your lenovo, for example, and install osx on it (assumeing it was compatible enough). It would be interesting to see if the opposite is true. maybe since the lenovo vista battery life is better than the mbp in vista, its osx life would also be better than the mbp. Reply
  • crispbp04 - Tuesday, June 16, 2009 - link

    Apple hardware optimized for Apple operating systems, and then comparing it to Vista running on the same device? Confused. Reply
  • flybefree - Tuesday, June 16, 2009 - link

    Here's your answer - we all know that Windows is completely bloated, inefficient operating system. Isn't this good supporting evidence to the fact? Reply
  • SoCalBoomer - Wednesday, June 17, 2009 - link

    No it's not good supporting evidence to that OPINION. Instead, it's comparing drivers made by Apple for its own operating system to drivers made by Apple for a competing operating system.

    Do you THINK Apple would optimize hardware drivers to get the best performance for WINDOWS? Are you NUTS?
  • JimmiG - Tuesday, June 16, 2009 - link

    On my netbook, I got about 30mins less battery life out of Ubuntu 8.10 LPIA version than Windows XP when browsing the net wirelessly. Much of this was due to the lack of power saving features in the drivers for things like audio, WLAN etc. Also CPU usage was generally higher and stayed at 100% more of the time. Of course, it might not be the same with full featured laptops, but I have a feeling Linux is no more efficient than Windows due to the poor driver support. Reply
  • nortexoid - Tuesday, June 16, 2009 - link

    It depends entirely on the driver support for your hardware and whether you compile the kernel yourself or whether you just use whatever some distro provides. With excellent manufacturer driver support and a self-compiled kernel, one should be able to obtain better battery life in linux than Windows XP. I mean, OS X IS based on freebsd, which is very similar to linux. Reply
  • SgtTech - Tuesday, June 16, 2009 - link

    I know this is not what this article was about but I bought the MacBook Pro 17" back in March. I have been pretty pleased with it except for one thing. I find that even the shorter battery life under Vista is still very good life as I get about 4-5 hours on my battery under email and web surfing conditions. However, I do have one problem in Vista 64 Bit, I consistantly have lockups, this started after about 3-4 weeks of no problems. Under OS X I have yet to have a lock up so I am pretty sure it is a driver. It gets worse as time goes on. I believe it is a NIC (wireless most likely) issue and am wondering if anyone else has experianced this and if you were able to resolve it. Currently I am trying to isolate it by disabling the wireless controller under Vista. Any help from the Anandtech crew would be helpful. Reply
  • nortexoid - Tuesday, June 16, 2009 - link

    I would be interested in a comparison with various distros of Linux (or just Ubuntu!) under gnome and KDE, using feature-comparable software (e.g. Rhythmbox and Epiphany/Firefox).

    I mean, what on Earth would be responsible for such a huge discrepancy between OS X and (every brand of) Windows?
  • MRC554 - Tuesday, June 16, 2009 - link

    Apple has total access to all Mac BIOS info - something Vista don´t have. With this extra advantage, Apple can optimize MacOS X for maximum energy consumption - something Vista can´t. That´s the reason MacOS X will always have better battery life on Macs. Reply

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