Thread: AMD Phenom 2

Just over a year back, AMD released a new processor family - codenamed Barcelona for servers, and Agena for desktops. The architecture was codenamed K1O. A lot of hope was pinned on the resulting Phenom processor range, but as we know they could not keep up with Intel's shiny new dual- and quad-core processors. Intel had a huge advantage with its Core architecture, timely revisions to the fabrication process and tweaks to the CPUs themselves - all of which kept the Core :2 based CPUs well ahead, in nearly all benchmarks. Intel also moved to a smaller, more efficient 45-nanometer fabrication process and promptly released new dual- and quad-core processors based on it. These were codenamed Penryn and quite frankly the performance gap just widened. AMD didn't have an answer to these CPUs and its dwindling presence in the desktop segment is testament to this fact. The battle between Intel and AMD could not have been more one-sided after Intel debuted its Core i7 architecture late last year. Industry experts believed this to be just one more nail in AMD's coffin and it's no secret that the Nehalem CPUs based on this architecture are currently the fastest desktop processors. Away from the limelight, and according to some, too weak to fight back, AMD quietly released its own 45nm counterparts late last year. These processors were named Phenom 2 CPUs and the architecture was codenamed Shanghai. AMD has been selling the concept of a computing platform for a while now and this makes sense both in terms of consumers as well as business profitability. Imagine an ecosystem provided by a single manufacturer - consisting of CPU, motherboard chipset and graphics solution. Any such platform can (obviously) be highly optimized and tweaked for maximum possible stability, performance and compatibility since one entity has control over development of all three components.

The first generation platform called Spider consisted of an AMD Phenom processor, a 790FX chipset motherboard and an ATi Radeon 3xxx series GPU The new platform, called Dragon, consists of an AMD Phenom :2 processor, a 790FX / 790GX / 790X motherboard and an ATi Radeon 4xxx series GPU. Architecturally speaking, Phenom 2 is not very different from the original Phenom. The most obvious difference from spec sheets is the huge increase in L3 cache. While Intel's Core i7 has eight MB of L3 cache, the Phenom had just two MB. On the Phenom :2 this has grown to 6 MB, meaning each core gets 1.5 MB of cache although this cache is common to all cores The Ll and L:2 caches remain identical to earlier Phenom processors. The other major advantage that Phenom 2 has is the fact that at 45nm, its die size is a lot smaller than the 65nm die of the Phenom. This allows these processors to scale higher clock speeds and cross the three GHz barrier - a feat Intel achieved awhile back.

The initial processors came with DDR2 memory controllers and were designed for AM2 and AM2+ sockets. This is another plus for AMD - no backward compatibility issues with newer processors and older motherboards. Newer Phenom processors for Socket AM3 motherboards have also made it 10 market and these processors have an upgraded memory controller that supports DDR2 as well as DDR3. And the beauty of this is that Socket AM3-based Phenom 2 processors can be used mAM2+ as well as AM3 boards Simply because the CPU sockets are pin-compatible. Of course there is a slight difference in the AM 3 processor's L3 cache and memory controller (these parts are collectively referred to as the uncore). They run at a speed of 2.0 GHz. The non-AM3 Phenom 2s run at a speed of 1.8 GHz. The DDR3 memory controller supports up to 1333 MHz memory clock speeds. On an . IM3 motherboard, the memory bandwidth is higher (21 GB/s as opposed to 17.1 GB/s). Since the AM3 socket also supports DDR2 memory speeds of up to 1066 MHz, motherboard manufacturers have an interesting choice of whether 10 provide a motherboard with DDR2 or DDR3 memory slots, or perhaps both, and this is where the platform's true flexibility hes. This is an attractive plus especially when compared 10 the competition. Intel has an LGA 775 interface for all its Core 2 Duos and Quads but the new Core i7 CPUs need investment in a completely new (and expensive) LGA 1366 motherboard, not to mention a mandatory investment in DDR3 memory - more arm-twisting due to near monopolistic market conditions7 In terms of clock speeds, the fact that AMD was able to scale its quad-cores up to 3.2 GHz from a previous high of 2.6 GHz was of interest to us; as was the jump from 65nm ,to 45nm since this brings its manufacturing process on a par with the competition. Earlier we felt that a meager 2 MB of L3 'cache was one of the chinks in Phenom's armour. The 6 MB cache on the higher end Phenom 2s would surely yield favourable results. Then there was the sudden til,t to DDR3. DDR3 offers greater bandwidth in comparison to DDR2. We're seeing faster, lower latency DDR3 chips slowly emerge and these CPUs could scale to higher performance levels with faster memory; of course, so would Intel's Nehalem.