Intel Core i5 and i7

At long last, a new mainstream CPU generation is upon us. Last year’s Core i7-900 series (Bloomfield) launch gave us our first taste of Intel’s latest microarchitecture, but those CPUs were unashamedly high-end and expensive. What we have now is Lynnfield, comparatively lower end but way more affordable. Lynnfield has launched in two varieties; the absolute mainstream Core i5-700 series and the mid-to-high-end Core i7-800 series (the i7-800s being clubbed with the i5s since they have way more in common with those than with the existing i7-900s—we’ll refer to them together as “Lynnfield”). 

To explain the new names a bit better: i7-900s replace older Core 2 Quads and XEs and are aimed at gamers and enthusiasts; i7-800s replace older high-end mainstream dual and quad-core CPUs for performance-minded users; and i5-700s target the same mainstream value-conscious buyers as the low- and mid-level Core 2 Duos. Going forward, the Core i3 brand will target entry-level users with low-cost chips. The i7-750 is priced at US$196 (approx Rs 9,450) and the i7-870 at US$562 (approx Rs 27,123) though Indian street prices will be known only in the coming weeks.

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What lies inside

All i-series Core chips are based on the new-gen Nehalem architecture, which moves most of a motherboard chipset’s guts onto the CPU package. This totally breaks compatibility with previous motherboards and chipsets, and for the first time in several generations, there are now different CPU sockets for the high end and mid-range—LGA1366 and LGA1156 respectively. Lynnfield CPUs will use LGA1156. For now, all iX-series CPUs are also quad core. At launch time, three CPUs are available, as explained in the table below: 

Click on the table for full-size

All Lynnfield CPUs will per force have to use the new Intel P55 chipset, which is the only platform capable of running them in their LGA1156 sockets. Just like the X58 for the i7-900s, there’s only one chipset and only one version of it. Lynnfield users will get most of the benefits of their high-end cousins, such as the integrated memory controller and IO subsystem, four cores with a huge shared L3 cache, the return of HyperThreading (on the i7-800) for more efficient multitasking, and most importantly the neat Turbo Boost feature which is a sort of reverse HyperThreading for boosting single-threaded apps. The main differentiator from the original Core i7-900s is that Lynnfield chips continue with a standard dual-channel RAM configuration rather than the triple-channel setup that feeds Bloomfield CPUs. They also have PCIe links for a discrete graphics processor rather than the rich QuickPath Interface (QPI) intended to connect multi-CPU Bloomfield configurations.

Where Lynnfield actually surpasses Bloomfield is the Turbo Boost feature. Turbo Boost basically panders to single-threaded applications by raising the speed of a single core (or two cores) when it detects that the rest are totally idle. As long as the cores collectively stay within the total heat and power envelopes they’re rated for, one core can actually jump significantly in speed. All of this is managed by a block of logic called the Power Control Unit. The Core i7-900s allowed one core to jump two multiplier notches up, or two cores to jump one notch up each. Lynnfield has a far more aggressive approach, and a core can reach around 20-25 percent higher speed under the right conditions. A single core can go four or more multipliers higher, and if heat isn’t a problem, all four cores can jump one or two speed bins as well. In absolute numbers, the Core i5-750 with a stock speed of 2.66 GHz can jump to 2.9 GHz with all four cores or as much as 3.22 GHz with a single core under stress. Think of it as selective, intelligent, official overclocking managed completely within the CPU, without any user intervention!

Lynnfield has one more surprise in store: Windows 7 is tweaked to work with its multiple cores and threads. Core Parking is a new technique to not only help applications make better use of available threads, but also prevent apps from jumping between cores (or background processes from needlessly occupying them) so that Turbo Boost can take full effect. This has the side effect of letting the CPU be more efficient, since unused cores can be powered down.

We’d be missing out if we didn’t talk a little bit about the P55 platform. Since so many of the chipset’s core guts have been moved onto the CPU die, this is the first single-chip solution from Intel for the mainstream desktop. That combined with the dual-channel RAM requirements and simpler circuitry should mean we’ll see some interesting microATX and maybe even ITX P55 motherboards in the coming months. There are no exciting new features such as SATA 3 or USB 3.0, but you’ll get the usual flavors of RAID, 14 USB ports, and Gigabit LAN. 

Performance

We set up the Core i5-750 and i7-870 on a Gigabyte P55-UD3R motherboard with 4 GB of 1600 MHz Corsair XMMS3 DDR3 RAM and a Radeon 4770 graphics card. Both processors were put through our entire benchmark suite, including synthetic tests, real-world tests, and 3D games. We were expecting high scores, but what we found was literally game-changing. In most tests, the i5-750 was as good as even the fastest Core 2 Quad Q9650. In gaming, where even the i7-900s didn’t show too much of an improvement over the Core 2s, Lynnfield excelled, most likely due to Turbo Boost. Considering it’s officially priced over 40 percent lower than the Q9650, the i5-750 seems to be a brilliant deal. 

Click on the table for full-size

There are even more surprises in store when we check out the i7-870’s scores: it actually beats the higher-ranked i7-900 series in many tests, and comes close to the i7-900 Extreme Editions. Again, it does so at a far more attractive price point.

Both CPUs run right over their top outside competition, the Phenom II X4 665 Black Edition, leaving AMD firmly in the dust, hopefully readying its own next generation CPUs.

Conclusion

The Core i5-750 brings devastating levels of performance to the mainstream market, and the i7-870 rivals the non-extreme edition i7-900 series at a far lower price. Combined with cheap RAM and motherboards, the Socket 1156 platform is looking mighty attractive, and Socket 1366 will probably be pushed into extreme performance territory: future 6-core Gulftown (Core i9?) and multi-CPU solutions only. Back at the mid-range level, Intel has effectively destroyed demand for most of its Core 2 series chips which plainly have no more headroom for growth. Turbo Boost is intriguing, and we’ll be running lots of tests in the near future to see exactly which types of applications benefit. And as for AMD, they might just have to go back to cutting prices and concentrating on the lower end for a while—only the top end Phenom II X4s can hope to compete.

Estimated Prices

Intel Core i7 965 - Rs 56,000
Intel Core i7 920 - Rs 14,900
Intel Core i5 750 - Rs 9,450
Intel Core i7 870 - Rs 27,100