|Name||CPU: Intel Sandy Bridge Core i5 2500k & Core i7 2600k|
|At a glance:||Quad-core (2500k) and quad-core with HyperThreading (2600k) CPUs,Works on new Socket 1155 motherboards,Unlocked multiplier for overclocking purposes|
|Summary:||A solid step forward for processors, both in terms of performance and bang-for-buck.|
This month for review we received two very eagerly awaited processors from CPU manufacturer Intel. Since AMD, its only real competitor, hasn’t been putting up a fight in this market for about five years now, interesting developments in CPUs have been few and far between. Will these Core i5 2500K and Core i7 2600K processors from the Sandy Bridge family of chips be revolutionary or just evolutionary?
Sandy Bridge is the latest ‘tock’ in Intel’s ‘tick-tock’ CPU microarchitecture strategy. For the uninitiated, the basis of this strategy is to release a new generation of CPU roughly every year, with one generation (the tick) being a shrink in manufacturing process of a previous CPU microarchitecture, and the next generation (the tock) being a shift to a new microarchitecture.
This tock succeeds the 45nm Nehalem microarchitecture (namely the Core i5 700 and Core i7 900 series) and its Westmere derivatives (such as the Core i3 500 and Core i5 600 series). This means that Sandy Bridge processors are built on a 32nm manufacturing process (a smaller process means more processing power can be packed into the same size chip, and it is more energy efficient). However, the chips have been radically updated meaning that clock for clock, and more importantly dollar for dollar, you’re going to get better performance out of this new technology.
Perhaps the most exciting aspect however is that Intel is releasing products for mainstream users first – the NZ$300 to NZ$600 market. This is good news because the last great mainstream product from Intel was released all the way back in September 2009, specifically the Core i5 750 quad-core CPU which clocked in at 2.66GHz and cost about NZ$400 on release. This chip was the ‘go-to guy’ for anyone building a gaming system or workstation. It provided decent performance but didn’t break the bank, and was only succeeded by the slightly faster Core i5 760 ten months after its release.
The chip about to take this mainstream crown, in my opinion at least, is the Core i5 2500K. Pricing may change by the time stock quantities stabilise in NZ but I think we’ll be looking at about $400 for the 2500K, which
is approximately the sweet spot for performance system builders, and $600 for its big brother the 2600K.
So what’s under the hood of these chips? In a nutshell the Core i5 2500K is a quad-core CPU running at 3.3GHz (although it can run up to 3.7GHz in Turbo Mode by disabling unused cores) and the Core i7 2600K is a quad-core CPU with HyperThreading (meaning each core can run two ‘threads’) running at 3.4GHz (or up to 3.8GHz in Turbo Mode).
Like most of the previous Westmere processors, Sandy Bridge also features a built-in graphics processing unit (GPU). However, now it’s actually part of the CPU die itself rather than being an extra chip crammed onto the PCB. The Core i5 and i7 ranges features the Intel HD Graphics 3000 GPU while the Core i3 range features the lower-specced HD Graphics 2000 GPU. To use this built-in GPU you’ll need a H67 Socket 1155 motherboard. The other option of motherboard, the P67 Socket 1155, requires a separate video card to be purchased but also supports SLI and Crossfire. And no, they’re not backwards compatible with any previous sockets/motherboards.
The ‘K’ at the end of each model number denotes the fact that both of these chips are multiplier-unlocked. All CPUs derive their operating frequency by taking the base system frequency (in this case 100MHz) and running at a multiple of this speed determined by the chip’s multiplier (33 for the 2500K and 34 for the 2600K, resulting in 3.3GHz and 3.4GHz respectively). Being ‘unlocked’ simply means you can change this multiplier to anything you fancy, all the way up to 57 for a whopping 5.7GHz CPU frequency, although you are extremely unlikely to get anywhere near this speed without a liquid cooling system and some serious voltage adjustments.
All Sandy Bridge chips without this K designation will be locked to run at their default multiplier – and you can’t overclock the base system frequency by more than 4–5%, unlike previous generations where you could sometimes even double this speed.
Unfortunately, of the two motherboards we received along with the chips, one was faulty and the other was running a beta version BIOS and didn’t seem to support overclocking at all, so I was unable to crank the speed up myself. Reports from the web suggest they are easily capable of 4.4GHz and above without any fancy cooling.
Being a proud owner of an older Core i7 920 CPU (a slightly faster version of which currently sells for approximately NZ$450) my first question was “how far outdated am I now?” so I put both of these processors to the test along with my CPU and the aforementioned Core i5 750. The tests chosen broadly represent the most common CPU-intensive tasks: Cinebench renders ultra high quality 3D images, 7-Zip is a file compression application (similar to Winzip), the x264 benchmark encodes HD video, and 3DMark 11 simulates 3D gaming.
A couple of points to note whilst looking at the results – firstly, the Core i7 920 is the only setup which used triple-channel memory, all the others used dual-channel (yes, Sandy Bridge sticks to dual-channel; a quad-channel platform is expected from Intel later this year). Secondly, remember that the Core i7 chips use HyperThreading, the Core i5 chips don’t (sometimes this improves performance, in other areas it can actually hinder it).
As you can see, there isn’t an earth-shattering improvement in any of the tested areas. The Cinebench rendering gets a rather healthy boost in both single- and multi-core tests (with HyperThreading helping considerably), linear improvements in the 7-Zip benchmark, a large bump in the first pass framerate of x264 encoding but not in the second pass, and nothing much worth mentioning in the 3DMark test except to say that it is a rare instance of the Core i7 920 keeping pace with the un-HyperThreaded Core i5 2500K.
Overall, these new Sandy Bridge processors represent a big step forward, as did previous new microarchitectures. The price point of the Core i5 2500K makes it particularly attractive, though, as it fairly convincingly outperforms the older, more expensive technology.
I wouldn’t go rushing out to replace your current Core i5 or i7 system, but if you have an older system that needs replacing, or if you’re building something new that needs decent horsepower, this range of CPUs is definitely what you should be looking at.
For benchmarks, check out February's issue of PC World!