Intel Lynnfield CPUs

Overview - the state of play
Intel launched the consumer-oriented Core i7 900-series processors back in November 2008, and the chip giant has known that it's been on to a winner with Nehalem, the codename for the underlying architecture. This is the reason we've seen little innovation on Core i7, and pricing has remained relatively steady since launch.

10 or so months later and no dramatic changes have been made. AMD continues to inch closer with a succession of higher-clocked, attractively-priced Phenom IIs X4s. Intel responds by snipping the price of various competing Core 2 Quad chips.

Now, countering AMD's growing threat, Intel brings a trio of what are known as Lynnfield chips to market. This TekSpek discusses what they are, how they're positioned, and how they're likely to be received.

The architecture
Intel is releasing the Core i5 750, Core i7 860, and Core i7 870 microprocessors. They're known by the codename Lynnfield and are presented on an LGA1156 form factor - the physical appearance of the chip package - which means they won't work in present X58 chipset-based boards used for LGA1366-based Core i7 900 chips.

When compared to present Core i7 900-series of chips the underlying architecture is kept intact, for the most part. All Lynnfield CPUs are based on a monolithic quad-core design, manufactured on a 45nm process, and ship with 1MB L2 and 8MB of shared L3 cache.

Further similarities extend to the feature-set, which includes SSE4.2 support, Intel SpeedStep Technology and 64-bit operation. Hyperthreading, too, is present on all chips bar the entry-level Lynnfield (Core i5 750).

Lynnfield, presented in a smaller CPU package (LGA1156), will share the Core i7 900-series' 700m+ transistor-count, as, noted above, much of the guts are the same. Indeed, the package is only smaller because of the lower pin-count; the silicon is the same, if not larger.

What's different?
DMI
Intel has had to reduce costs in the transition to Lynnfield. From an architecture point of view, then, Lynnfield chips will interface with the system via a DMI (Direct Media Interface) conduit rather than QPI found on Bloomfield - the codename for Core i7 9xx chips. QPI has greater bandwidth and provides processor-to-processor support in a multi-socketed system. Lynnfield is aimed squarely at the client market and the substituting of DMI for QPI should make little performance difference.

PCI-Express
Adding in a neat trick, Intel is plumbing 16 PCI-Express lanes - used primarily for graphics - right into the new chips, rather than have a separate bridge handle the duties. What this means is that the chips' supporting core-logic, P55, also new, doesn't require an IOH bridge-chip, as found on presently-available X58 boards.

The relative bandwidth limitations on having two x8 PCIe slots may well affect the performance of high-end multi-graphics-card setups from ATI and NVIDIA, however. The X58 is better in this regard, obviously, but comes at a higher cost - around £130 for a no-frills mainboard, compared to £85 for the cheapest P55.

Dual-channel memory Current Bloomfield chips use a tri-channel memory-controller that provides excellent bandwidth. Testing has shown that the processors are relatively memory-agnostic, working almost as well in dual-channel mode - helped on, no doubt, by the large 8MB of L3 cache. Lynnfield drops the third memory channel and runs a regular dual-channel memory setup.

Intel, though, adds official DDR3-1,333 support (and only DDR3) for Lynnfield parts, up from DDR3-1,066 on most Bloomfields, helping bridge some of the pure bandwidth disadvantage.

Lower power-draw
Intel, too, has dropped the power-draw of the Lynnfield range from 130W to 95W, and it will introduce low-power versions of the Core i5 750 and Core i7 860, pulling a maximum 82W, rather than 95W.

Enhanced Turbo Boost
The Turbo Boost feature has been enhanced for Lynnfield. The premise behind it is to ensure that compute power is kept to a maximum as long as it fits inside the chip's TDP.

Core i7 900-series chips can increase their frequency by one 'multiplier' (133MHz) if running all four cores, and by two for applications taking advantage of one or two cores. Lynnfield increases four-core load by two steps (266MHz), dual-core processing by four steps (533MHz) and single-core usage by five steps (666MHz). That's impressive 'factory-overclocking' considering the 95W TDP.

Evaluated on a clock-for-clock basis against Bloomfield, Lynnfield chips lose a little speed, due to a lack of a third memory channel and QPI, but introduce a more-robust Turbo Boost feature that's inextricably allied to a lower power-draw.

Stacking them up

Speed and branding
The top three rows denote Lynnfield CPUs. Intel's revised nomenclature is such that Lynnfield is productised as either Core i5 and Core i7 - the latter also being concurrently used for Bloomfield-based chips.

It's the model-numbering system that sets them apart. The entry-level Core i5 750 stands as the budget part because its performance is somewhat hampered by the lack of Hyperthreading support, evinced in heavily multithreaded scenarios. This is an intentional ploy on Intel's part, to differentiate the range, and to keep models' performance from overlapping.

The Core i7 800-range includes the 860 and 870. The chips are separated solely by clockspeed, with the former clocking in at 2.80GHz and the latter at 2.93GHz.

Incumbent Core i7 900-series will continue to use the establishing model-numbering systems, but the actual numbers don't line up with the Lynnfield 800-series. For example, a Core i7 960 (Bloomfield) is clocked in at 3.20GHz, whereas the Core i7 860 (Lynnfield) runs at 2.80GHz.

Value proposition?
Retail-boxed Core i5 750s should ship for around £139. The pricing brings AMD Phenom II X4 and lower-end Core 2 Quads very much in the firing line, deliberately so, and the basic specification of the chip suggests it will do quite well at this price point.

Core i7 860, clocked in at 2.80GHz - rising to 3.46GHz under Turbo Boost - is to be priced identically to the slightly slower-clocked Core i7 920 that's been out a while. AMD's Phenom X4 965 BE appears to be a target, as well as mid-range Core 2 Quads.

Pricing for the Core i7 860 is bemusing, set to £385 and matching Core i7 960's, which is an intrinsically better chip.

Performance
Independent testing shows that Core i5 750 is a match for both AMD Phenom II X4 955/965 Black Edition (£150/£175) and Intel Core 2 Quad Q9650 (£220) chips.

The Core i7 860, evaluated over a wide range of benchmarks, beats out any CPU available from AMD and trades blows with the volume-selling Core i7 920, whilst the Core i7 870 is a touch faster than Core i7 920 but slower than Core i7 950. Confusing, eh?

Range upheaval
Introduction of three new CPUs based on the potent Nehalem architecture - two costing less than £200 - means that the Intel Core 2 Quad's lifespan will be curtailed. It is expected that Intel will sell current stock but move on to Lynnfield production which should be cheaper for all £100-plus chips by mid-2010.

Complicating matters, Intel will also introduce a bevy of 32nm-based chips, codenamed Westmere, to fit on to the same LGA1156 package as these Lynnfield CPUs. Limited to dual-core, quad-threaded models in the first instance, they will feature integrated graphics as standard.

The summary
The three new Intel's Lynnfield chips help cement the company's position as the provider of the fastest consumer processors. Starting at around £140 for the base model, Core i5 750, and rising to £385 for the Core i7 870, the trio of models compete well against the established Core 2 Quad, Core i7 900-series, and AMD's Phenom II X4 CPUs.

Stressing value, the Core i5 750 and Core i7 860 provide stern competition in the sub-£200 space. Both chips can be coupled with <£100 motherboards for a mid-priced build. The Core i7 870 isn't such a good buy, offering scant additional performance over the 860 part but costing almost twice as much.