Testing by Ryan Shrout, written by Josh Walrath.

Introduction

    The original Phenom II redesign (Deneb) on 45 nm gave AMD the product which could match Intel in terms of overall performance with the older Core 2 Quad series of parts.  Unfortunately for AMD, the Intel i7 series proved to be far too powerful of an opponent to overtake.  The Phenom II has had a good run though, and it has kept AMD as a contender in the CPU field.  Now that Intel has fleshed out the rest of its Nehalem family and is slowly phasing out the Core 2 products, AMD was left with a stagnating product landscape.

    The Phenom II X4 series has topped out at 3.4 GHz and looks to potentially go no further.  The Athlon II series of parts (X2, X3, and X4) have proven to be affordable and popular products that have carved out a solid marketplace in the budget sector.  AMD certainly needed something to keep the company relevant in the face of Intel’s ever expanding family of fast Nehalem based processors.  AMD also needed something to compete with Intel’s recently released i7-980 Extreme, which is a 3.33 GHz 6 core processor that has ruled the performance roost.  But if there were one downside to the i7 980, it is the price.  Originally released at $999, most retailers have raised that price fairly significantly.

    On the server side AMD has kept pace with Intel, and in fact had released the first 6 core product in the Summer of 2009.  The original “Istanbul” core powered the latest Operton processors with speeds up to 2.8 GHz for limited edition parts.  The majority of these products were clocked below 2.6 GHz, but they proved to be popular for their low overall TDP and processor density.  AMD knew it had the basic design to compete with Intel on the high performance desktop, but more work had to be done to get it ready for that platform.

The Thuban core and AMD's 6-core gamble

    From Istanbul to Thuban.  Even though these two places are light years away from each other, the design that AMD has produced for both of these chips is nearly identical.  Internally they are the same, but of course externally they do have some differences.  Thuban will reside in a 938 pin chip package with one HT 3.0 connection while Istanbul is in Socket F form with 1207 LGA pads.

    AMD focused on power efficiency as well as potential clockspeed targets close to that of the previous Deneb/Shanghai processors.  On the desktop Deneb was able to hit 3.4 GHz with a TDP of 140 watts, but that later shrunk to 125 watts with the Revision C3 parts.  With Thuban being about 25% bigger in terms of die size and transistor count, it was initially thought that it would be unlikely that AMD would be able to make a 3 GHz+ part and reach the same TDPs as Deneb.

    AMD had two advantages over Deneb and its TDP/clockspeed combination.  Time and process enhancements.  AMD was able to take the initial Shanghai/Deneb design, and really optimize the architecture to retain its clockspeed but also improve power properties.  AMD implemented more aggressive power saving routines and work out some of the troublesome spots on the original design.

    The other aspect, which is process changes, is probably more significant than the design changes.  GLOBALFOUNDRIES, previously the manufacturing arm of AMD, has a long history of injecting new technologies into current process nodes to improve overall switching and power performance.  They have done this extensively through the years, and they continue to do this on their latest 45 nm SOI process.  The chips coming off of the 45 nm line today are more power efficient and have the ability to clock higher than the original Phenom IIs released in January, 2009.  Thuban is a beneficiary of this process enhancement.  Apparently AMD has included a Low-K Di-electric material in the design, which improves leakage while not significantly affecting transistor switching performance.  This has allowed AMD to lower the TDP of this part as compared to what it could have been if the design had been left unchanged from Shanghai as well as using the older iteration of the 45 nm process.  This is not the only process change that GF has applied to their 45 nm SOI, but it is the most significant.

    In the end we are faced with a product with a 25% larger die size, but is able to clock to the same speeds as the previous Deneb processors, all the while retaining a 125 watt TDP rating.  The 3.2 GHz Phenom II X6 is officially named the Phenom II X6 1090T.  At first glance one would think that this chip has little to offer people who will not utilize all six of those cores as compared to the much cheaper Phenom II X4 955.  This is not correct.

Turbo Core

    AMD let this little number slip earlier this month, and this can be viewed as a “poor man’s Turbo Boost”.  Intel released Turbo Boost with their i7 processors, and it basically overclocks individual cores to higher clockspeeds, depending on the TDP properties of the chip as a whole.  For example one core is clocked an extra 266 MHz while the rest of the cores go into a low power mode, or are stopped altogether.  Two cores can be clocked up 133 MHz a piece if the processor detects if those cores are the ones being highly utilized.  Intel’s Turbo Boost is a very granular solution which really accentuates the performance of the i7 across a large number of workloads.

    Turbo Core takes that idea, but simplifies it.  Instead of controlling the turbo functionality on a per core basis, AMD splits the cores into two categories; those to be overclocked and those to be put into a C1E low power mode.  If the processor determines that three or fewer cores are being fully utilized, it will overclock those cores by 400 to 500 MHz.  The other three go into their low power mode and are clocked to 800 MHz.  This keeps the TDP around 125 watts.  This can give a nice boost in performance when dealing with applications not leveraging four or more cores.

    The Phenom II X6 1090T can boost its clockspeed from 3.2 GHz to 3.6 GHz, while the 1055T can go from 2.8 GHz to 3.3 GHz.  Apparently enough changes were made internally to the chip that waking up the different cores is fast enough that thread switching from core to core does not significantly impact overall performance, and the advantages of running at 400 to 500 MHz faster outweigh that of the small latency of waking up and clocking up the individual cores.

OverDrive Update

    AMD is constantly updating its OverDrive software suite, which makes overclocking Black Edition processors a breeze.  It supports the new 1090T processor, and it really is the only way to adequately check if Turbo Core works.  This also controls the North Bridge speed of the Processor, as well as memory and HyperTransport speed.

    Motherboards need to support AOD (AMD OverDrive) to get it to work.  Certain memory manufacturers have also released “Black Edition Profiles” that maximize performance of their DIMMS when used with AOD and Phenom II processors.