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Socket AM3: AMD's Phenom II Gets DDR3

Inside AM3

AMD’s AM3-ready Phenom II processors are very much similar to the existing AM2/AM2+ Phenom II chips.

Socket AM2+on Asus' M3A79-T

Each core includes 64 KB of L1 data cache and 64 KB of L1 instruction cache, totaling 512 KB per quad-core processor. Each core also includes 512 KB of L2 cache, adding up to 2 MB per X4 and 1.5 MB per X3 CPU. Then, depending on the model, you get 4 MB or 6 MB of shared L3 cache.

The chip’s memory controller is where you’ll see the real difference between today’s Phenom IIs and the chips launched back during CES. The 128-bit controller remains, interfacing with two 64-bit channels of memory. Whereas the previous Phenom IIs ran their controller at 1.8 GHz, all AM3 processors support up to 2 GHz speeds. AM3 extends memory support to include DDR3-1333 modules in addition to the DDR2-1066 ceiling of the previous generation. Interestingly, if you choose to run DDR3-1333 modules, you’ll be limited to a single DIMM per channel, making your memory purchase particularly critical.

With the increase in memory controller speed comes a faster HyperTransport interface—from 1.8 GHz to 2 GHz as well, upping theoretical bandwidth to 33.1 GB/s from 31.5 GB/s.

That the AM3-able Phenom II, etched on AMD’s 45 nm DSL SOI process, is approximated at 758 million transistors in a 258 square millimeter package makes it clear that these new CPUs employ the same silicon as the existing Phenom II X4 940/920s. The issue, of course, is the socket. With a 940-pin array, there’s no way to shoehorn one of the old AM2/AM2+ processors into the new AM3 socket. Officially, AMD says it’ll update its lineup with faster parts in the near future. But we’re fairly impatient, so we’re going to try to get our AM2+ Phenom II running on the new socket interface today, instead.

Socket AM3 on Asus' M4A79T Deluxe


The Phenom II goes a long way to improve AMD’s standing against Intel with regard to power consumption. First and foremost, the design enables four p-states, rather than just two. As a result, at idle, the Phenom II chips in our launch review throttled all the way down to 800 MHz. Power consumption dropped in kind, and AMD’s newest design proved itself a much more energy-efficient contender than its predecessor.

At the same time, AMD changed previous power-saving functionality that let each core enter p-states independently. When a thread began on a core running at half-speed, performance naturally suffered. Now, with Phenom II, all four (or three) cores run at the same frequency. But increased granularity in the number of p-states translates into a much better balance between speed and power-savings.

The last Phenom chip in AMD’s armada was the Phenom X4 9950 Black Edition running at 2.6 GHz. That processor was rated at a 140 W TDP, which you’ll remember caused trouble when it was discovered that some inexpensive motherboards weren’t designed to accommodate the increased load and would invariably fail. Shifting to 45 nm immersion lithography helped AMD rein in power consumption with Phenom II and the 3 GHz X4 940 featured a 125 W TDP. All of the AM3-ready chips announced today yield further savings given their 95 W TDPs.

Chris Angelini is an Editor Emeritus at Tom's Hardware US. He edits hardware reviews and covers high-profile CPU and GPU launches.
  • kelfen
    Cheering the underdog in hopes for better compitition to benifit the consumer!
  • groo
    I sure don't see the point of spending cash on DDR3 unless you are also spending cash on i7. I woudn't mind a CPU that can handle DDR3 in the future, but there sure isn't a reason toupgrade to it at today's memory prices.
  • Aatish
    nice review... but....
    strangely AMD is performing better than core i7 920!
    what did I miss? in previous benchmark done by you guys showed AMD performing quite less than what I see in this benchmark! can anyone clear my confusion? please!:)
  • Commlock
    Very good test indeed that shows, IMHO, to go with an overclocked Core i7 if DDR3 is to be preferred. Otherwise, sticking with DDR2 RAM, an AM2+ MoBo and A Phenom II 940-like CPU seems the best optimized system. However, concerns can be put forward on the continuity of the system in couple of years' time, where simply upgrading without major component changes can be discussed.
  • sohei
    an AM2 mobo is compatible with AM3?
  • I understand the fact that you guys compare cpu's in the same price region plus whats available to you and the socket upgrade and all that. But i would really like to see how the AMD 940 Black Edition compare to Intel Corei7 EE 965. And maybe include the corei7 940 to. An all out performance battle with just the benchmark figures that counts
  • waffle911
    The 940 runs at 3 GHz. The 920 and 720 both cruise at 2.8 GHz. But the 910, 810, and 710 all run at 2.6 GHz. There goes the idea that each increment of 10 corresponds to 100 MHz. The 805 chugs along at 2.5 GHz.
    Looks to me like every increment of 10 in the designation yields a 200MHz clock increment, and 5 being 100MHz. But then either the 940 should actually be the 930. Then again, Volvo's recent product nomenclature doesn't add up, either. the V50 is the wagon variant of the S40, and the V70 was the wagon variant of the S60, but is now of the new S80. But they can't change it to V90 because then the Cross-Country variant of the V70 would have to be called he XC90 instead of XC70—but they already have an XC90 SUV. Digging themselves into a hole of consumer confusion, AMD and Volvo both.

    But why is AMD shafting early adopters by shutting out AM2+ PhenomII from the AM3 platform without even offering an AM3 920/940?
  • Well, can't agree with socket chart.
    Let's see (long run)
    AMD&Intel: Socket 7 (intel up to some 266MHz?, AMD up to 550MHz)
    Intel Slot 1 - with FCPGA adapters up to some 1200MHz?
    AMD SlotA - with socketA adapters up to some 1600MHz?
    PPGA s370 ~ 600MHz?
    FCPGA (coppermine) 1100MHz
    FCPGA2 (tualatin) 1500MHz?
    Guess what...PPGA/FCPGA/FCPGA2 were the same socket (s370).
    Now...SocketA ranged from 800MHz Durons to 2GHz AthlonXP 3200+
    P4 start was with socket 423, but intel soon abandoned it for 478, however there were some adapters for some CPUs which allowed s478 CPUs to work on s423 mobos.
    AMD with A64 introduced single channel DDR platform on s754. Later in 939 there was enhancement with dual channel and dual core. But then DDR2 appeared with quite low prices - so they moved to AM2.
    Intel brought LGA775, but most chipsets for Prescott couldn't handle Core 2, later C2D FSB800MHz chipsets couldn't handle FSB1066 and 1333MHz C2D/C2Q cpus. And now we get LGA1366, 1156 and some more for the same familly. Well, I guess intel is more disruptive than AMD. I can put PhenomII 810 AM3 to my AM2 mobo on M1695+NF3, some NF3 ASRock users can do that too. AM2/2+/3 is on the best way to be worthy SocketA successor.
  • raden_muaz
    I've been waiting for so long for this phenom ii to come.
    At last, phenom beats i7 in some kind of way.

    Anyway, I never bought Intel for years because:
  • sohei
    there are 5 sokets technically but 2 physically
    my question is : somebody try a am2/am2+ with a am3 cpu?