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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  • Jamahl - Monday, January 4, 2010 - link

    If this is a sign of things to come from intels 32nm, AMD must be laughing their asses off.

    Every one of these cpu's is an overpriced piece of garbage.
  • ereavis - Monday, January 4, 2010 - link

    Phenom II X2 550 should be on this list, it's the direct competitor to the i3 -- dual core with real cache. It beats the Athlon II X4 processors and the Athlon II X2 don't even belong.
  • ereavis - Monday, January 4, 2010 - link

    blasted no edit function. The 550 is also about the same price point.

    Guess I didn't combine criticism with the fact that this review was exactly what I've been waiting for and very well written, I like the added IGP page as I'm sitting on a 785 IGP while discrete cards are in between releases. All of which may get passed on to my mom's dying Sempron if an I3 deal pops up.

    Also minor correction, the Phenom II 925 is an X4. Where are the release dates?
  • SilentSin - Monday, January 4, 2010 - link

    I second your question to Intel about the pricing of the 32nm i5 chips...who the hell is going to buy that? The i3's are looking pretty sweet as an alternative to an AMD HTPC platform at that low price point, though. March should make for an interesting competition once AMD launches their new RD890G (4350 based) chipsets. I'm guessing those will thoroughly trounce the GMA part on these chips as well as having quite a few features that the Intel HD stuff can't do, but at least Intel put something up that isn't completely laughable for once.
  • Cogman - Monday, January 4, 2010 - link

    x264 is NOT a codec. Let me repeat that, x264 is NOT a codec. It is an ENCODER. The video output from x264 is in the H.264 standard (or codec if you like).

    Saying that x264 is an alternative to H.264 is retarded. It isn't an alternative, it USES the H.264 standard. Its like trying to say that mySQL is an alternative to the Ansi SQL standard. It isn't an alternative, it is an implementation of it.
  • puffpio - Monday, January 4, 2010 - link

    hahaha..that always gets on my nerves too!
    but you can take it as a compliment that x264's popularity is strong enough that people mistake it for h264..

    people make the same mistake with divx, kleenex, qtip, xerox, etc...
  • Anand Lal Shimpi - Monday, January 4, 2010 - link

    My apologies for sounding like a fool :-) I've updated the text. I just meant that it was an alternative to closed source H.264 encoders but my phrasing was absolutely horrendous for that purpose.

    Thanks for pointing out the error :)

    Take care,
  • proneax - Monday, January 4, 2010 - link

    I would like to see you measure the power consumption on the DH55TC using the integrated graphics.

    Legitreviews shows Idle/Load of 49/99W for the 661 in that setup.
  • Anand Lal Shimpi - Monday, January 4, 2010 - link

    Agreed - I'll do it as soon as I'm back in the office. Just gotta survive CES :)

    Take care,
  • medi01 - Monday, January 4, 2010 - link

    Dual core 3.3Ghz CPU + Radeon 5870 consuming only 110 watt at load???

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