AES-NI: Much Faster Encryption & Bitlocker Performance

Westmere (and thus Clarkdale) adds some new instructions to x86, although the big expansion comes with AVX and Sandy Bridge next year. Westmere gets six new encryption/decryption instructions. The group of instructions accelerate AES (Advanced Encryption Standard) and are thus referred to as AES-NI.

Many businesses require that all corporate PCs have the contents of their hard drives encrypted through the use of software like Bitlocker that comes with Microsoft Windows 7. These sorts of applications can be accelerated by AES-NI and to show the potential benefit I dug up a test I did while preparing for one of our SSD articles several months ago.

If you turn on Bitlocker in Windows 7 there's an immediate and measurable impact to performance. Disk performance generally drops by a noticeable amount and actual application usage performance drops by a smaller amount. Every write to the disk has to be encrypted first so there's some obvious CPU overhead. Clarkdale should reduce that overhead significantly as the common encryption operations are now hardware accelerated.

To test this I ran three tests. I first ran PCMark Vantage's HDD suite on my Windows 7 testbed SSD (an OCZ Summit) on a Core i5 661, then encrypted the drive using Bitlocker and ran the same test on the same processor. For the last test I swapped out the i5 661 for a Lynnfield based Core i5 750 (no AES-NI) and re-ran the HDD test. The results below were quite promising:

Processor PCMark Vantage HDD % of Unencrypted Performance
Clarkdale - Unencrypted 16713  
Clarkdale - Bitlocker Encryption 13785 82.5%
Lynnfield - Bitlocker Encryption 11744 70.3%


There's a definite benefit to Clarkdale's AES-NI instructions. There's still a performance hit from enabling Bitlocker, but it's not nearly as great as on Lynnfield and other architectures that don't have AES-NI support. With a smaller decrease in I/O performance from enabling full disk encryption, there's also a smaller hit to application performance as well. This is huge for corporate desktops/notebooks.

Most of those machines aren't quad-core encoding monsters; they use dual-core processors. The upgrade from Core 2 seems like it'd be worth it, or at least AES-NI will probably keep AMD out of the running for consideration.

Intel HD Graphics: A Lot Better ASUS Saves the Day: Simulated Core i3s & The Test
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  • Paladin1211 - Monday, January 4, 2010 - link

    On page 13, in WoW benchmark, the Core i5 750 outperforms the Core i7 870 by more than 30% (92.3 fps vs 70.6 fps). Anything wrong here?
  • Crimson67 - Tuesday, January 5, 2010 - link

    WoW doesn't seem to like hyperthreading, it's the only explanation
  • ereavis - Wednesday, January 6, 2010 - link

    is it using the hyperthread core on the 870 but a true core on the 750? That would certainly slow it down. If it's using a true core on both it should be better still.
  • Dyzios - Monday, January 4, 2010 - link

    Remember NVIDIA Hybrid idea, to have two GPUs ? - one weak for 2D/light 3D graphics and powerful discrete GPU for gaming? Those CPU makes sense for this approach - however Radeon 5870 also has good point with optimized low idle power consumption. Maybe still there is point as even Radeon cannot go very low as GPU on-die. The only question is to have capability to switch HDMI output between on-die GPU and discrete.I wonder how this works currently - still needed to stick to DVI output from Radeon or can be combined?
  • Zool - Tuesday, January 5, 2010 - link

    If the 40nm 5600 series cards will show the same improvments in power usage than the 5800 series than u can forget the intels GMA graphic.

    I think that for a 2D card/3D discret card u can buy a mobo with a dirty cheap intel GMA on it clocked much lower if u realy need.
  • silverblue - Wednesday, January 6, 2010 - link

    The graphics comparison isn't exactly fair but in the end, it's not something AMD should be too worried about. The i5-661, with its 900MHz 45nm GPU, is being compared to the old 790GX's HD 3300 which operates at 700MHz on a 55nm process. I admit, in the benchmarks we're talking the best i5 vs. the best AMD has to offer, but considering...

    a) the relative performance of the i5-750 as compared to the PII X4 965 which is usually manifested as an advantage
    b) the fact that the 32nm i5s can increase their core speed by 133MHz and 266MHz thanks to Turbo depending on the number of active cores
    c) most games still aren't designed to take full advantage of multithreading so four cores may not yield a tangible performance increase

    ...then AMD's still in the lead for IGPs. If the 3300 had been clocked at 900MHz, would it have lost even one of the listed benchmarks? I'm not sure it would have. What's more, we're still talking a 55nm part; we all know of TSMC's issues with the 40nm process and AMD going fablress, so is it unreasonable to expect that AMD could move their IGP production en masse to 40nm with TSMC or 45nm with GlobalFoundries?

    In closing, it's a big step forward for Intel, however if AMD came out with a higher clocked 40/45nm IGP then, Sideport or not, new tech or not, AMD would be far ahead, at least on gaming terms. Sideport does very little for the performance of current AMD IGPs, anyway.

    I just wish AMD were able to release a Clarkdale competitor sooner rather than later.
  • ruetheday - Friday, January 8, 2010 - link

    the IGP on Clarkdale isn't maxed out at 900Mhz; It too can be overclocked significantly. Here's an article on techgage showing an OC to 1133, for example.

    Remember that Intel is very conservative on binning parts to ensure no issues with reliability over time (compare vs nvidia mobile gpus).
  • silverblue - Friday, January 8, 2010 - link

    Maybe so, however a 40/45nm AMD part could reach similar clockspeeds. I just don't think that, clock for clock, the new Intel IGP on the Clarkdale die is as powerful as anything AMD or nVidia can produce on the same scale. It's a good step forwards, just not the leadership that some may have been expecting.
  • silverblue - Wednesday, January 6, 2010 - link

    Slight mistake... second best 32nm i5 that Intel has to offer. However, I doubt the performance increase over the 661 will be very noticable with the IGP; won't it be clocked the same in both?
  • Zool - Monday, January 4, 2010 - link

    The irony is the biggest drawback of these cpu-s is the 45nm intel graphic on other die with the memmory controler. The die savings from 45nm vs 32nm are quite big.
    If they would make just 32nm dual core nehalem with memory controler on die it would be still much smaller(and only litle bigger than the clarkdale without imc) than the GMA die with memmory controler.
    The whole thing would be solved with everything as one on 32nm.
    I think plenty of people just wait for 32nm quad core nehalems without the useless GMA graphic.
    Actualy what is the cost of dirty cheap GMA in penryn based 3 package boards. Like 5-10 dolars ?

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