Shanghai represents AMD's first major speed update in a while, with the clock ceiling raised from 2.3GHz to 2.7GHz across the entire Shanghai product line. The average power utilization for even the fastest Shanghai CPU remains the same as Barcelona's 75 watts, while 55 watt and 105 watt parts will appear in 2009. A 105-watt Shanghai brings to mind a factory-overclocked CPU specially tuned for sci/tech, high-performance computing, and workstations. That's just my guess. I think that AMD wants to make it clear that while it is taking a fresh run at the 2P market, it still rules the roost in high performance x86 computing.

Sublimely green

Shanghai took advantage of a smaller manufacturing process (thinner wires, smaller transistors) to make room for a healthy 6MB of Level 3 cache while supplying each core with an independent 512KB Level 2 cache. The precision of AMD's Immersion Lithography process reduces transistor power leakage, giving rise to AMD's claim of a 35 percent reduction in idle power utilization relative to Barcelona. Lowering the idle power floor makes the dynamic power management capabilities first seen in Barcelona really shine.

Another feature new to Shanghai is Smart Fetch, which allows cores to spend more time in a halted state by copying cores' L1 and L2 cache contents to Level 3 cache before halting them. AMD says that this happens transparently and that it lowers CPU power consumption by up to 21 percent, but I hope to see it surface as runtime down-coring, in which unneeded cores can be powered down under user control. Taking a 2P Shanghai system sublimely green would be to down-core it to two cores (one per socket), powering up new cores as needed.

In discussions about Shanghai, AMD refers to Barcelona the same way that Intel once tipped its hat to the short-lived 32-bit Core Duo (Pentium M) CPU. AMD credits Barcelona for shouldering the "heavy lifting" in Shanghai's design, which was considerably sweetened by process shrink and other enhancements. The way Barcelona went down made no one happy -- not engineers, not management, and certainly not OEMs. Shanghai should set all of that right again with a newfound commitment to stay in close touch with OEMs and major accounts.