Intel's X25-M 34nm vs 50nm: Not as Straight Forward As You'd Think

It took me a while to understand exactly what Intel did with its latest drive, mostly because there are no docs publicly available on either the flash used in the drives or on the controller itself. Intel is always purposefully vague about important details, leaving everything up to clever phrasing of questions and guesswork with tests and numbers before you truly uncover what's going on. But after weeks with the drive, I think I've got it.

  X25-M Gen 1 X25-M Gen 2
Flash Manufacturing Process 50nm 34nm
Flash Read Latency 85 µs 65 µs
Flash Write Latency 115 µs 85 µs
Random 4KB Reads Up to 35K IOPS Up to 35K IOPS
Random 4KB Writes Up to 3.3K IOPS Up to 6.6K IOPS (80GB)
Up to 8.6K IOPS (160GB)
Sequential Read Up to 250MB/s Up to 250MB/s
Sequential Write Up to 70MB/s Up to 70MB/s
Halogen-free No Yes
Introductory Price $345 (80GB)
$600 - $700 (160GB)
$225 (80GB)
$440 (160GB)

 


The old X25-M G1


The new X25-M G2

Moving to 34nm flash let Intel drive the price of the X25-M to ultra competitive levels. It also gave Intel the opportunity to tune controller performance a bit. The architecture of the controller hasn't changed, but it is technically a different piece of silicon (that happens to be Halogen-free). What has changed is the firmware itself.


The old controller


The new controller

The new X25-M G2 has twice as much DRAM on-board as the previous drive. The old 160GB drive used a 16MB Samsung 166MHz SDRAM (CAS3):


Goodbye Samsung

The new 160GB G2 drive uses a 32MB Micron 133MHz SDRAM (CAS3):


Hello Micron

More memory means that the drive can track more data and do a better job of keeping itself defragmented and well organized. We see this reflected in the "used" 4KB random write performance, which is around 50% higher than the previous drive.

Intel is now using 16GB flash packages instead of 8GB packages from the original drive. Once 34nm production really ramps up, Intel could outfit the back of the PCB with 10 more chips and deliver a 320GB drive. I wouldn't expect that anytime soon though.


The old X25-M G1


The new X25-M G2

Low level performance of the new drive ranges from no improvement to significant depending on the test:

Note that these results are a bit different than my initial preview. I'm using the latest build of Iometer this time around, instead of the latest version from iometer.org. It does a better job filling the drives and produces more reliable test data in general.

The trend however is clear: the new G2 drive isn't that much faster. In fact, the G2 is slower than the G1 in my 4KB random write test when the drive is brand new. The benefit however is that the G2 doesn't drop in performance when used...at all. Yep, you read that right. In the most strenuous case for any SSD, the new G2 doesn't even break a sweat. That's...just...awesome.

The rest of the numbers are pretty much even, with the exception of 4KB random reads where the G2 is roughly 11% faster.

I continue to turn to PCMark Vantage as the closest indication to real world performance I can get for these SSDs, and it echoes my earlier sentiments:

When brand new, the G1 and the G2 are very close in performance. There are some tests where the G2 is faster, others where the G1 is faster. The HDD suite shows the true potential of the G2 and even there we're only looking at a 5.6% performance gain.

It's in the used state that we see the G2 pull ahead a bit more, but still not drastic. The advantage in the HDD suite is around 7.5%, but the rest of the tests are very close. Obviously the major draw to the 34nm drives is their price, but that can't be all there is to it...can it?

The new drives come with TRIM support, albeit not out of the box. Sometime in Q4 of this year, Intel will offer a downloadable firmware that enables TRIM on only the 34nm drives. TRIM on these drives will perform much like TRIM does on the OCZ drives using Indilinx' manual TRIM tool - in other words, restoring performance to almost new.

Because it can more or less rely on being able to TRIM invalid data, the G2 firmware is noticeably different from what's used in the G1. In fact, if we slightly modify the way I tested in the Anthology I can actually get the G1 to outperform the G2 even in PCMark Vantage. In the Anthology, to test the used state of a drive I would first fill the drive then restore my test image onto it. The restore process helped to fragment the drive and make sure the spare-area got some use as well. If we take the same approach but instead of imaging the drive we perform a clean Windows install on it, we end up with a much more fragmented state; it's not a situation you should ever encounter since a fresh install of Windows should be performed on a clean, secure erased drive, but it does give me an excellent way to show exactly what I'm talking about with the G2:

  PCMark Vantage (New) PCMark Vantage HDD (New) PCMark Vantage (Fragmented + Used) PCMark Vantage HDD (Fragmented + Used)
Intel X25-M G1 15496 32365 14921 26271
Intel X25-M G2 15925 33166 14622 24567
G2 Advantage 2.8% 2.5% -2.0% -6.5%

 

Something definitely changed with the way the G2 handles fragmentation, it doesn't deal with it as elegantly as the G1 did. I don't believe this is a step backwards though, Intel is clearly counting on TRIM to keep the drive from ever getting to the point that the G1 could get to. The tradeoff is most definitely performance and probably responsible for the G2's ability to maintain very high random write speeds even while used. I should mention that even without TRIM it's unlikely that the G2 will get to this performance state where it's actually slower than the G1; the test just helps to highlight that there are significant differences between the drives.

Overall the G2 is the better drive but it's support for TRIM that will ultimately ensure that. The G1 will degrade in performance over time, the G2 will only lose performance as you fill it with real data. I wonder what else Intel has decided to add to the new firmware...

I hate to say it but this is another example of Intel only delivering what it needs to in order to succeed. There's nothing that keeps the G1 from also having TRIM other than Intel being unwilling to invest the development time to make it happen. I'd be willing to assume that Intel already has TRIM working on the G1 internally and it simply chose not to validate the firmware for public release (an admittedly long process). But from Intel's perspective, why bother?

Even the G1, in its used state, is faster than the fastest Indilinx drive. In 4KB random writes the G1 is even faster than an SLC Indilinx drive. Intel doesn't need to touch the G1, the only thing faster than it is the G2. Still, I do wish that Intel would be generous to its loyal customers that shelled out $600 for the first X25-M. It just seems like the right thing to do. Sigh.

Used vs. New Performance: Revisited All Indilinx Drives Are Built Alike
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  • Anand Lal Shimpi - Monday, August 31, 2009 - link

    Intel insists it's not an artificial cap and I tend to believe the source that fed me that information.

    That being said, if it's not an artificial cap it's either:

    1) Designed that way and can't be changed without a new controller
    2) A bug and can be fixed with firmware
    3) A bug and can't be fixed without a new controller

    Or some combination of those items. We'll see :)

    Take care,
    Anand
    Reply
  • Adul - Monday, August 31, 2009 - link

    Another fine article anand :). Keep up the good work. Reply
  • CurseTheSky - Monday, August 31, 2009 - link

    This is absolutely the best article I've read in a very long time - not just from Anandtech - from anywhere.

    I've been collecting information and comparing benchmarks / testimonials for over a month, trying to help myself decide between Intel, Indilinx, and Samsung-based drives. While it was easy to see that one of the three trails the pack, it was difficult to decide if the Intel G2 or Indilinx drives were the best bang for the buck.

    This article made it all apparent: The Intel G2 drives have better random read / write performance, but worse sequential write performance. Regardless, both drives are perfectly acceptable for every day use, and the real world difference would be hardly noticeable. Now if only the Intel drives would come back in stock, close to MSRP.

    Thank you for taking the time to write the article.
    Reply
  • deputc26 - Monday, August 31, 2009 - link

    been waiting months for this one. Reply
  • therealnickdanger - Monday, August 31, 2009 - link

    Ditto! Thanks Anand! Now the big question... Intel G2 or Vertex Turbo? :) It's nice to have options! Reply
  • Hank Scorpion - Monday, August 31, 2009 - link

    Anand,

    YOU ARE A LEGEND!!! go and get some good sleep, thanks for answering and allaying my fears... i appreciate all your hard work!!!!

    256GB OCZ Vertex is on the top of my list as soon as a validated Windows 7 TRIM firmware that doesnt need any work by me is organized....

    once a firmware is organised then my new machine is born.... MUHAHAHAHAHAHA
    Reply
  • AbRASiON - Monday, August 31, 2009 - link

    Vertex Turbo is a complete rip off, Anand clearly held back saying it from offending the guy at OCZ.
    Now the other OCZ models however, could be a different story.
    Reply
  • MikeZZZZ - Monday, August 31, 2009 - link

    I too love my Vertex. Running these things in RAID0 will blow your mind. I'm just waiting for some affordable enterprise-class drives for our servers.

    Mike
    http://solidstatedrivehome.com">http://solidstatedrivehome.com
    Reply
  • JPS - Monday, August 31, 2009 - link

    I loved the first draft of the Anthology and this is a great follow-up. I have been running a Vertex in workstation and laptop for months know and continue to be amazed at the difference when I boot up a comparable system still running standard HDDs. Reply
  • gigahertz20 - Monday, August 31, 2009 - link

    Another great article from Anand, now where can I get my Intel X-25M G2 :) Reply

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