Intel Sandy Bridge Core i5-2500K & Core i7-2600K Processors Review

Author: MAC
Date: January 2, 2011
Product Name: Intel Core i5-2500K & Core i7-2600K
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Sandy Bridge: Intel Core i5-2500K & Core i7-2600K

Sandy Bridge/Gulftown/Clarkdale/Lynnfield/Bloomfield - Click on image to enlarge

Over the last 2 years we have witnessed the release of 4 new processor families based on the Nehalem microarchitecture, and we would be hard pressed to hide the fact that we've enjoyed the journey. The Core i5 and Core i7 processors were substantial improvements over the venerable Core 2 processors that had been the stalwart of most enthusiast's systems during the second-half of the decade. As good as Nehalem-based processors are though, Intel's Tick-Tock strategy never ceases to push CPU technology forward, and that has brought us to today's launch of Intel's brand proressor microarchitecture, Sandy Bridge.

4 cores/8 threads - 8MB L3 Cache - 995 Million Transistors - 216mm2

While it would be tempting to describe this new microarchitecture as a hybrid between Lynnfield (advanced Turbo features/power management) and Clarkdale (integrated GPU/32nm process), Sandy Bridge represents an equal if not greater change than we saw going from Core 2 to Nehalem. The cores have been totally redesigned, the front-end branch predictors have been optimized, all the parts of the chip are connected via a high bandwidth 256-bit ringbus, the L3 cache now runs at full speed and its latency has been lowered, the memory controller frequency has increased dramatically, and there's even a new extension in the form of AVX, Advanced Vector Extension. This all combines to create a microarchitecture that is on average 10-20% faster than what is currently on the market, and that can peak at over 40% faster in certain workloads.

We obviously can't talk Sandy Bridge without mention the integrated GPU. This new IGP is an evolution of the one found in Clarkdale chips, it does feature reworked cores, but it benefits most greatly from the 32nm manufacturing process and the new ringbus interface. The process shrink has permitted Intel to increase the IGPs clock speed dramatically (up to 1.35Ghz!) while continuing to have a minimal impact on overall power consumption and heat output. If you want to know more, click here to jump to our Intel HD Graphics 2000/3000 section.

Now before we start talking about the individual models in the new Sandy Bridge family, let's reiterate the Core i3/5/7 naming scheme that Intel has chosen to continue with this new release. Simply put, Core i7 models are eight-thread processors which feature both Hyper-Threading (HT) and Turbo Boost technology. The Core i5 models are four-thread processors with Turbo Boost. The Core i5 series will continue to be particularly confusing to consumers though, since it is comprised of both 4-core/4-thread and 2-core/4-thread processors. Lastly, there is Core i3 series models, which are 2-core/4-thread processors but without Turbo Boost.

Enough talk for now, here is how the new Sandy Bridge family breaks down:

This is what we are going to call the 'mainstream' models. On one end, the Core i5-2400 effectively slots into the spot previously held by the Core i5-750, while on the other end, the Core i7-2600K can be seen as replacement for the Core i7-875K. As you can see, the Turbo Boost implementation is nowhere near as aggressive as with Lynnfield, but the default clock frequencies are quite a bit higher.

Here we have the more affordable, budget-friendly Sandy Bridge variants. While somewhat attractively priced, these chips are going to face enormous competition from AMD processors like the upcoming Phenom II X4 840.

Last, but certainly not least, are these low wattage beauties. These are the models that are likely going to prove very popular with the HTPC crowd, or just those that keep a watchful eye on their electricity bill.

A new product lineup always mean new packaging, and Intel have indeed unveiled a new look for their Sandy Bridge processors:

Core i5-2500K on the left, Core i7-2600K on the right - Click on image to enlarge

Here is Sandy Bridge in the flesh. As you can see, unless you are truly astute, these new LGA1155 Sandy Bridge processors are almost indistinguishable from the previous LGA1156 Clarkdale and Lynnfield models.

Based on the digits on the integrated heatspreaders, we can determine that these two chips were made in the 35th and 37th week of 2010. That might seem kind of old considering that we are now in 2011, but Intel is known for stockpiling millions of chips before a launch.

LGA1155 vs. LGA1156 vs. LGA1156 - Click on image to enlarge

Once again, even from the back, Sandy Bridge is almost indistinguishable from Lynnfield and Clarkdale, but Intel have moved the securing notches to ensure that no one can have any installation mix-ups/disasters.

Don't expect to ever see stock clocks with Turbo Boost enabled - Click on image to enlarge

With Sandy Bridge, Intel has integrated the clock generator off the motherboard and onto the processor itself. The most visible aspect of this change is that the 'bus speed' has been reduced from 133Mhz to 100Mhz. However, the tangible effect is the BCLK overclocking issue that have been reported over the last few months. There is a very little BCLK headroom on Sandy Bridge processors, roughly 5% to 10% maximum. This is because so many of the CPU's different parts are deriving their operating frequencies from this base clock, and since some are very sensitive to frequency changes, they can get out of whack very quickly.

Although Sandy Bridge is manufactured on the smaller 32nm process, operating voltages haven't decreased much (if at all) when compared to the 45nm Lynnfield chips. This really isn't a bad thing though, since Intel is using that voltage to produce SB processors with higher clock speeds.

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