Phenom II 955 Black Edition

Tweaking the Core
There were quite a few enhancements applied to the original Phenom core, and to leave it unmodified would simply unjustify the II moniker. The most important one is AMD's tweaked Smart Fetch technology, which is essentially how the three levels of cache interact with each other. Each core on the quad-core Phenom II has exclusive access to their own pools of L1 cache (at 64kb data, and 64kb instructions), as well as L2 cache (512kb). There's a giant collective pool in the centre of the chip that is comparatively mammoth, running 6MB of cache.

The differences here are that each progressive level runs slower than the preceding levels, meaning that the largest cache is also the slowest. This is minimised by the Smart Fetch tech, which is essentially a process where the data kept in the L1 and L2 caches are mirrored on the L3 cache - in case of a core halt (otherwise known as an execution error) the data is already waiting to be replicated. Smart Fetch isn't just a mirror however and constantly monitors what data should be kept in the cache, as well as what data might be needed in the future. All these add up to some decent performance gains, as well as reliability.

Micromanaged Microarchitecture

The Phenom was a breakthrough chip when first released, being the first true Quad-core CPU to include four cores on the one die. The downsides to this were noticed significantly at launch before the manufacturing process was tweaked well enough for high yields, and if a single core is damaged on the die then the entire chip will be faulty (though the triple-cored CPUs can sometimes work if the faulty core is disabled with a laser).

Thanks to their smart design, individual cores can lower their clockspeeds and core voltage when at idle to save power. The Phenom II brings something new to the table however; new CoolCore technology means that the L3 cache can also be shut down when not in use. Considering that this part of the die is the same amount in terms of real estate as the cores themselves, this is a great innovation that should save a little extra power.