Phenom II X6 and its flagship 1090T
If you've been following the development of AMD's K10 and K10.5 processor architecture you're going to feel right at home in this review. Why? Because AMD's new Phenom II X6 series, or future Phenom II X4 T for that matter have little architecture changes over the "old" Phenom II X4 processors. Sure, AMD added two more physical cores which is of course a big deal, but other than that, AMD just used all of the potential of K10.5 that was already there. There's also another interesting feature that will help Phenom II X6 to shine no matter the workload environment. All together, what AMD produced this time is very a powerful and flexible processor, and yet very affordable. But let's take it apart from the bottom to top.
First off, many of you Socket AM2+/AM3 users will be very happy to hear that the new Phenom II X6 series is compatible with older existing motherboards as long as you have a BIOS update that adds Phenom II X6 support and power regulation strong enough to support 130 W processors. So if you already own an AM2+/AM3 motherboard, check out your vendor's CPU support list, maybe you're in luck, or rather you should be in luck because at this moment there are close to 200 motherboard models supporting Phenom II X6.
That being said, you can pair up the new Phenoms with either 1066 MHz DDR2 or 1333 MHz DDR3 memory, using the integrated dual channel memory controller, the same one as in other Phenom II processors, possibly with some minor tweaks and optimizations for six cores.
Now that we mentioned those six physical CPU cores, you have to know that it's not groundbreaking stuff for AMD as they shipped their first Istanbul six core server processor almost a year ago, and they've taken some good time to adapt that server version for desktop users. On the other hand, there was no real rush in getting out six core processors, as desktop applications rarely make good use of quad core processors. The end result, and product we have in our hands today is codenamed Thuban. As mentioned before, it bears a lot of similarities with the existing Phenom II line-up. Each of the six processor cores has 128 KB of L1 cache, a total of 512 KB per core of L2 cache and they all share a big pool of 6 MB of L3 cache. Now that pool could have been bigger, or rather it should be bigger for six cores, and together with dual channel memory it presents a possible bottleneck in performance with heavy threaded tasks. But then again, redesigning the memory controller or cache buffer would not make Phenom II X6 such an affordable buy.
The list of supported features and implemented technologies is the same as on older Phenom II models, with just one major difference, called TurboCore. This time it's AMD that copied some solutions from Intel, but unlike Intel who has designed its Core ix architecture to work with Turbo Boost from the start, AMD sort of forced this feature into new Phenom II X6 models. The purpose is the same as with Intel's Turbo Boost, to raise the frequency of few cores when the processor is not fully loaded, it's just that the process of boosting the clocks is somewhat different, limited by an architecture not designed for such a feature. Nevertheless, AMD did a great job considering the space they had to work with.
To begin with AMD re-introduced the possibility of adjusting the core speed of individual cores, a feature that caused some performance bugs in original Phenom I processors. This time in Thuban, the ability to adjust individual core clocks is used to automatically overclock cores under load if three or more cores are in idle state. The more cores sit at idle, the bigger the overclock on those under load will be. In theory it's the same thing just like Intel's Turbo Boost, but unlike Intel, AMD can't shut down idling cores or regulate the voltage individually per core. This means when you load up a single threaded application, Turbo Core will boost the voltage on ALL cores and overclock the core under load until the TDP limit of 125 W is reached. If two or more cores are loaded, with at least three cores still in idle, Turbo Core overclock will be reduced because 125 W TDP will be reached faster, especially with all cores, including those at idle running at increased voltage. The good thing is that cores siting in idle are clocked down to 800 MHz, but are still receiving boosted voltage. If you manage to load more than three cores, Turbo Core will automatically be disabled and all cores will run at stock speed with stock voltage.
Other than this feature, Phenom II X6 is no different from other Phenom II or Athlon II processors, as far as the list of implemented technologies and instructions goes. The ones that really matter can be seen on CPU-Z screenshot below.
With additional two cores, Thuban grew from 258 mm² (Deneb) to 346 mm² in die size, and is now counting an impressive 904 million transistors. It's built on AMD's 45 nm manufacturing node and will be the foundation for all Phenom II X6 models in the near future, and new quad core models 900 T that are due to be introduced soon (two disabled cores). So far, AMD introduced just two Phenom II X6 models, 3.20 GHz 1090T Black Edition with unlock multiplier and a slower version clocked at 2.80 GHz, called 1055T.
With the core count bump you'd expect TDP to hit the 140 W limit again, just like the first version of Phenom II X4 965 did, but in that case you'd be very wrong. In past AMD reviews we've always checked the lower limit of core voltage where processor are still fully stable, and results have always been very impressive, often reaching near 1.1 V with stock frequency. It seems AMD now has more confidence in manufacturing quality and the new C3 revision because both 1090T and 1055T models work with significantly lower voltages compared to older C2 revisions of Phenom II and especially Athlon II models. The tested model, 1090T Black Edition, works at very high 3.20 GHz clock speed using just 1.300 V on core voltage, resulting in very acceptable 125 W TDP. Things change when Turbo Core kicks in, and all cores get a voltage bump to 1.450 V, enabling some of the cores to reach 3.60 GHz which is the maximum Turbo Core overclock. That speed is very rarely reached even when just one core is under load, and with multiple cores under load Phenom II X6 1090T averages around 3.40 GHz which is still a great result for AMD's first six core desktop processor. It's going to be very hard to outperform Intel's very high clocks with Turbo Boost in single threaded applications, so every little bit will definitely help.
When idling, Phenom II X6 1090T might even surprise you with very low power consumption comparing to other Phenom II X4 models, thanks to its lower operating core voltage, and enabling C'n'Q you can save quite a bit of power if your computer spends much time in idle. But then again, that's not why you would buy such a power horse like Phenom II X6. With its attractive suggested price point of $ 295 AMD clearly aims to do some damage in market segments ruled by Intel until now. It's not going to be easy against potent Core i7 860 or sturdy Core i7 920/930, but this time AMD is looking well equipped for the battle.
Together with the new Phenom II X6 series, AMD introduced and new chipset logic to go together with their new processors. The AMD 890FX is an evolution of the 790FX chipset while using the same manufacturing node, and providing the same features and number of PCI-E lanes (44x PCI-E 2.0). One difference is IOMMU that can boost some device performance mostly in virtualization environments. You can find more information on AMD's IOMMU here. Another difference is the updated chipset bus (connection between the IOMMU and southbridge), the ALink III, which is essentially a PCI-Express 2.0 x4 link, having a total bandwidth of 4 GB/s. This is double that of the ALink II used in 790FX (PCI-Express 1.1 x4), which has a total bandwidth of 2 GB/s.
Also new here is the small southbridge chip named SB850. With it AMD offers native SATA 6 Gb/s support (six ports), 14 USB 2.0 ports, older PCI interface, HD Audio controller and Gigabit Ethernet support. ALink III makes sure that the chipset bus doesn't become a bottleneck for the SATA 6 Gb/s controller, especially in heavyweight RAID 5 modes involving solid state drives. And yes, if you're wondering, disabled CPU cores can still be unlocked even on new chipsets using implementations by motherboard vendors.