Finally Phenom(enal) ?

AMD touts its Phenom 2 processors as a return to competition. We check the validity of this bold statement.

Just over a year back, AMD released a new processor family — codenamed Barcelona for servers, and Agena for desktops. The architecture was codenamed K10. 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.

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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 L1 and L2 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 2 processors for Socket AM3 motherboards have also made it to 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 in AM2+ as well as AM3 boards simply because the CPU sockets are pin-compatible. Of course there is a slight difference in the AM3 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 AM3 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 to provide a motherboard with DDR2 or DDR3 memory slots, or perhaps both, and this is where the platform’s true flexibility lies. This is an attractive plus especially when compared to 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 conditions?

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 meagre 2 MB of L3 cache was one of the chinks in Phenom’s armor. The 6 MB cache on the higher end Phenom 2s would surely yield favorable results. Then there was the sudden tilt 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.

So we wrote to AMD asking for the newest 3.2 GHz Phenom 2 955 BE. The BE suffix signifies a black edition. This means that the CPU multiplier is unlocked — a boon for over lockers, especially if the motherboard does not have much potential for over clocking its FSB/HTT. We also asked for a motherboard based on the new AM3 platform and we were sent a Gigabyte GA-MA790FXT-UD5P based on the 790FX.

This is a very well laid out and solidly built board, with an all solid-state capacitor design. There’s even a small heat sink provided for the additional SATA controller that provides four SATA ports in addition to the SB750s (Southbridge) six. One of the talked-about inclusions in terms of features was EC AOD-ACC — an acronym for “Embedded Controller for AMD OverDrive-Advanced Clock Calibration” that is part of the new Southbridge and allows AMD Black Edition CPUs to be over clocked. The BIOS is rich with over clocking options, although you do need to know exactly what you’re doing. AMD also sent us DDR3 memory in the form of two sticks of Corsair Dominator memory rated at 1600 MHz at timings of 9-9-9-24 and a voltage of 1.65. We were also sent an ATi HD 4890 graphics card, although for all the graphics related tests we stuck to our reference NVIDIA GTX 285 solution for the sake of uniformity. Also in the box, was a small but efficient CPU cooler.

Once everything was setup we noticed how cool the processor was running. With the room at an ambient 25 degrees, the CPU went to 37 degrees and stayed there for a good while. Upon stress-benchmarking, we noticed a rise of not more than nine degrees and this testifies to the fact that the 45nm Phenom 2 is a lot cooler than the 65nm Phenom processors, even at a much higher clock speed. For the record we did manage to over clock this processor to a stable 4.1 GHz using air-cooling, and although the temperature soared to 56 degrees it was obvious that with a better cooling solution we could crack 4.8 GHz easily, however we didn’t push it. So AMD’s Phenom 2 over clocks well, but how did it do on stock?

The Phenom 2 955 BE is just about available here and its pricing is not stable at the moment. We expect it to fall to around the Rs. 14,000 mark but the best we could find was Rs. 15,000 making it costlier than the Phenom X4 9950, but cheaper than the Rs. 17,000 Intel Core 2 Q9550 (2.83 GHz). As the benchmarks show (note the bold figures indicate the best performer) this CPU actually takes the lead in a couple of benchmarks and this is astounding given the company it’s in. On the whole, it’s still much slower than the mighty Core i7 965 Extreme and quite a bit behind the Core 2 Extreme Q9770, but it trounces the Core 2 Duo Q8200, something the Phenom X4 9950 wasn’t able to achieve; this proves AMD is finally on the right track. The optimizations to the Barcelona core, the extra L3 cache, the improved clock speeds and its excellent thermal characteristics are testament to a great product. It is however, nearly twice the price of the Q8200 and we could not get our hands on either a Q9450 (2.66 GHz) or a Q9550 (2.83 GHz) both of which are similarly priced and therefore more comparable. Our intuition tells us that this CPU will come very close to the Q9550 and perhaps beat the Q9450 in a good many benchmarks. This is high praise for a company that six months back seemed to have no hope of providing even cursory competition to Intel. AMD’s fortunes have far from changed, after all Intel has promised 32nm Nehalem variants in early 2010, but the Phenom 2 marks the beginning of renewed hope for the green team. After all, everybody likes a good fight.