In the year since Intel released the Nehalem-EP quad-core Xeon CPU, all the
hubbub surrounding that chip and its new design has proven accurate. Bigger,
better, faster, more -- a whole lot more than anything that Intel had ever
released before. But that was then, this is now, and as they say, what have you
done for me lately?
Today, the Nehalem-EP gives way to the Westmere-EP, or X5600-series Xeon CPU.
Whereas the Nehalem was a big-time performance bump over the previous
generation, the Westmere is a more incremental and predictable improvement, but
it's definitely a better chip. Westmere picks up where Nehalem left off.
[ Also on InfoWorld: Intel's Westmere and AMD's Magny-Cours will change the face
of IT forever. See "Modern multicore and the next generation of IT." ]
The key developments in Westmere-EP are two more cores (six total), the ability
to address two DIMMs per channel at 1,333MHz, a 50 percent larger L3 cache, a
set of instructions (AES-NI) for accelerating AES encryption, and better CPU
power management. Westmere is the equal of Nehalem in single-threaded workloads,
but far more scalable thanks to the additional two cores per die. The speed of
Westmere's encryption operations will also turn heads.
In fact, the 400 percent performance increase shown with the AES-NI instructions
makes whole-disk encryption almost unnoticeable. Previously encryption required
a fairly sizable performance trade-off, but with the Westmere's AES performance
jump, it becomes a no-brainer. And that's just one of many potential use cases
of the AES-NI features.
The Westmere is built on the same basic guidelines as the Nehalem -- integrated
memory controller, shared L3 cache per socket, and QPI (QuickPath Interconnect)
-- but it's based on a 32nm process rather than Nehalem's 45nm. It runs up to
3.33GHz per core, and two threads per core with Hyper-Threading. That's 24
logical CPUs in a two-socket system, all balanced against 6.4GT/s QPI. It's
definitely fast, but not terribly so when compared to Nehalem CPUs running at
the same clock speed.
Like Nehalem, Westmere implements Turbo Mode to ramp up the clock speed on
certain cores depending on load. Turbo Mode benefits single-threaded and lightly
threaded applications by increasing the performance of a few cores when needed.
Also, Westmere CPUs sit in the same sockets as Nehalem CPUs. In fact, some
Nehalem-based mainboards can support Westmere already, possibly requiring a BIOS
update. This isn't true of all Nehalem systems, however, so do some research
In a bid to reduce power consumption, Westmere CPUs can essentially gate off
unused cores and shut them down to reduce power, saving their state in cache.
Yes, Nehalems can do this too, but Westmere chips can also gate off the uncore,
or the region of the CPU that is tasked not with central processing but with
memory control and L3 cache, bus controllers, and so on. Whereas a Nehalem could
power gate each core, the Westmere can power gate everything, which has the
benefit of reducing power draw at idle.