Phenom II Architecture Improvements and Advances in 45nm
Rather than going through Phenom’s architecture in detail, we would encourage you to check out our Phenom X3 review that was published a few months ago. We go through many of the architectural advancements over the K8 Hammer architecture.
To put it simply, Phenom II is not just a die-shrink, but rather a significant core revision. AMD’s 45nm SOI process has allowed AMD to make some important Phenom improvements. The first is not really an architectural improvement, but rather an enabler. AMD’s 45nm immersion lithography has allowed Phenom II to be produced with higher frequencies, tighter tolerances and less current leakage compared to its predecessor. This – especially the higher frequencies – is all very welcome news. The second most significant addition is the 300% increase in L3 cache memory, which is 6MB up from only 2MB. The significant reduction in core size has undoubtedly allowed AMD to squeeze more cache memory into the Phenom II. The L2 cache remains as-is at 512KB per core.
The improvements don’t end there though. There are several other core improvements including the following:
- L3 cache latency reduced by 2-cycles compared to the 65nm Phenom L3
- Increased DRAM bandwidth
- Cache flush on halt: The core’s L1 and L2 flush into shared L3 after a core enters a halt state allowing the core to drop to a lower speed and save power
- Path-based indirect branch prediction
- 2x increase in core probe bandwidth
- Larger load/store buffering / larger floating point buffering / reduced MAB (missed buffer) lifetime
- Improved LOCK pipelining: (LOCK is an instruction prefix) this improves performance when multiple LOCKS are in process simultaneously
- FP MOV compute optimization: Floating point register-to-register move instruction improvements
We’re not going to get too heavily into the inner architectural workings of a CPU, but it is pretty safe to say that AMD’s 45nm Phenom II is designed to be more efficient when compared clock-for-clock to the older 65nm Phenom. We’ll be comparing equally clocked Phenom and Phenom II processors in our performance testing to see just how significant these changes are.
Aside from performance related improvements, there were also some pretty significant power saving features implemented into Phenom II, namely Cool’n’Quiet 3.0. AMD tells us that additional power states reduce idle power of the Phenom II by as much as 40% and also reduces power consumption under moderate loads.
One particular point of interest that came straight from AMD is the following: “Massive headroom using extreme and experimental cooling techniques”. This is straight from the horse’s mouth, and some preliminary overclocking results that have popped up across the web have definitely validated this claim. AMD’s Phenom II loves the cold, which is something that could not be said for Athlon X2 and 65nm Phenom processors. We expect to see a healthy resurgence of interest in the AMD overclocking scene, and some heavier duty overclocking oriented motherboards hitting the market.
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