It was literally a week before we received our Phenom samples that many within AMD learned of a serious erratum in the processor that could potentially have a significant impact on system stability or performance, depending on how it was handled. Microprocessor erratum are quite common - no CPU is perfect and many are patched with fixes for these erratum through BIOS updates throughout the life of the CPU.

However, every now and then an erratum comes along that is a little more dangerous, its impact a little more serious, and that's when microprocessors either get recalled or tackled by a software workaround immediately. Phenom hardly had a smooth launch and its traction in the marketplace has been nearly nonexistant, partially because of the TLB issue but also because of a relative inability to compete, even with AMD's own dual-core products in many cases.

AMD is looking to relaunch Phenom this year with a new revision of the core and higher clock speeds. This new core was designed specifically to address the TLB erratum that crept up late last year and we managed to get our hands on a pre-release sample from one of AMD's partners before final production samples shipped. What follows is a quick explanation of the erratum and a look at how, and if, the B3 stepping core does indeed fix things.

Phenom needs help and B3 would at least be the first step towards giving it some much needed aid.

The "TLB Bug" Explained


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  • aguilpa1 - Thursday, March 13, 2008 - link

    It has already been done. There are tons of sites that have already benchmarked the Phenom (errata fix disabled) against the core 2. Fixing the TLB via hardware doesn't magically make it any faster. There is only a slight increase but its not significant.

    Redoing all the benchmarks just to prove a slight increase but still lagging behind overall is just beating a dead horse at this point.
  • crimson117 - Wednesday, March 12, 2008 - link

    Clock for Clock is an irrelevant metric. So what if 2.0GHZ on a C2D is faster than 2.0GHZ on a Phenom?

    Performance per Dollar or Performance per Watt are much more relevant metrics.
  • backtomac - Wednesday, March 12, 2008 - link

    All those metrics are important. Each individual will have a differing importance on each metric.

  • flipmode - Wednesday, March 12, 2008 - link

    Says you. It's relevant to at least two people here. Reply
  • JarredWalton - Thursday, March 13, 2008 - link

    Actually, I'd say clock-for-clock is one of the worst comparisons to make, short of two things:

    1) If available clock speeds are similar (they're not - Core 2 Quad tends to have about a 33% advantage in clock speed)
    2) If you want to look purely at the architectural performance

    While item two looks interesting at first, you have to remember that architecture and design ultimately have a large impact on clock speed. Which is better: more pipeline stages and higher clock speeds, or fewer pipeline stages with lower clock speeds? If you think you know the answer, go work for Intel or AMD. In truth, there is no correct answer - both approaches have merits, and so we end up with a balancing act.

    Pentium 4 (NetBurst) is often regarded as going too far in the way of pipeline stages. Which Prescott certainly had some problems due to the pipeline stage count, Northwood and the current Penryn are actually not that far off in terms of stages. The difference is that Penryn (and Core 2 in general) have made numerous changes to the underlying architecture that makes the pipeline stage count less important now.

    Clock for clock, I'd imagine an updated 486 core could compete very well in today's market. That is, IF you could actually make such a core. Just think about it: four pipeline stages, give it some more cache, add in SSE and x64 support, put two or four cores on a chip, and then run that sucker at 3.0GHz! But each stage is the old 486 requires so much work to be done that you could never actually get such a design to scale to 2.0GHz on current technology, let alone 3-4GHz.

    So when someone says clock-for-clock comparisons are irrelevant, I largely tend to agree. Why don't we do a "clock-for-clock" comparison of a tractor-trailer diesel engine and a formula one engine? Or a "clock-for-clock" comparison of apples and oranges? The latter takes things to an extreme to illustrate a point, but in the case of the former all you really could end up determining is that large diesel engines and racing engines are vastly different.

    K10 and Penryn might not be quite so different, but they are dissimilar in enough ways that the best way to compare them really ends up being a large selection of real world performance metrics. Sure, a 2.4GHz Penryn and a 2.4GHz Phenom X4 gives us some idea of how the designs match up, but at the end of the day what really matters is price, performance, stability/reliability, and power requirements (the latter also impacting noise).
  • flipmode - Sunday, March 16, 2008 - link

    Whether or not there is value in comparing IPC is pretty subjective. I happen to disagree with you - I find it valuable, at least for the time being while both AMD and Intel are offering CPUs at comparable clockspeeds (1.6GHz to 3.2GHz, generally). If AMD's were all less than 2.5GHz and Intel's were all more than 2.5GHz then it would be much less useful info to me to know how they performed at the same clockspeed since they didn't operate at the same clockspeed. But it's not the end of the world if Anandtech chooses not to look at such things. Reply
  • mindless1 - Friday, March 14, 2008 - link

    Clock for clock is quite relevant because prices change and people overclock. It doesn't mean someone only picks which has more performance per MHz or which has higher MHz or any such thing, rather within a family it is quite relevant to know how it performs clock per clock then the user does the math to further evaluate other alternatives. Reply
  • murphyslabrat - Wednesday, March 12, 2008 - link

    However, it does give a foundation for comparing prices and clockspeeds not explicitly compared. It also helps to evaluate potential gain from overclocking.

    You are right, there are better methods. This one (clock-for-clock performance), while not a very valuable metric in and of itself, does allow better extrapolation.
  • Cygni - Wednesday, March 12, 2008 - link

    Its called a PREview for a reason. ;) Im sure there will be AT rundown of the chip later. This short blurb is only to tell us about the TLB fix. Reply

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