Westmere vs. Nehalem
Westmere - more of the sameThe tick-tock model means that a process-shrink follows a new architecture. Nehalem was the new architecture for 2009 and we covered it in detail here. Summarising for brevity, the 45nm Nehalem core improved upon Core 2 in a number of meaningful ways. The incumbent front-side bus of Core 2 - often a bandwidth bottleneck - was removed and effectively replaced by an integrated triple-channel memory-controller and QuickPath Interconnect (QPI).
Nehalem also brought with it four-issue processing, a three-tier cache hierarchy, including all-inclusive 8MB of L3 cache, and, boosting performance further, simultaneous hyper-threading - similar to that used on the Pentium 4 range of chips. The native quad-core Nehalem CPUs were equipped with eight processing cores, then, and the modular nature of the design, split into what were termed 'core' and 'uncore', meant that chips with different core-counts could be manufactured far more easily than with Core 2.
Then there was Turbo Boost, made possible by a sophisticated on-chip power-control unit, which increased core(s)' speeds depending upon workload, to the extent that the chip's TDP limit was reached. All very clever, absolutely, but not exactly aimed at the mainstream and budget user.
The new architecture comfortably outperformed Core 2 on a clock-for-clock basis and therefore remained a high-end part - codenamed Bloomfield, based on an LGA1366 form factor - for almost a year.
Intel then distilled Nehalem into more mainstream quad-core parts known as Lynnfield, castrating them somewhat with the removal of the third memory channel and replacement of QPI by a DMI interface. The newer LGA1156-based Lynnfield chips, complete with a more-robust Turbo Boost feature, have represented Intel's upper mid-range offerings for Q4 2009.
The Westmere architecture, which contains the all of the performance characteristics of second-generation Nehalem (Lynnfield core), and built on a smaller-transistor 32nm process, enables Intel to use the potency of Nehalem in a smaller die area. Intel goes further and reduces the physical core count on all Westmere chips from four to two, leading to a significantly smaller die-size. You'll see why this is important in a moment or two.
New features for 32nm process - AES
Westmere is, strictly speaking, a superset of Nehalem. The silicon contains six new instructions incorporated to increase the speed of Advanced Encryption Standard (AES) encryption and decryption. Termed AES-NI and remembering that the new architecture is designed to cover server, desktop and client, Intel thinks that hardware-based encryption/decryption - security, in other words - is a worthwhile area in which to invest logic. The popular file-compression program WinZip 14 contains AES encryption, and our testing has shown Westmere to be 2.5x faster than Nehalem at the task.
