Intel Core i7-870 review

Darien Graham-Smith October 7, 2009

£439

Price when reviewed

The Core i7-870 is Intel’s fastest CPU based on its new Lynnfield core (the lesser models being the Core i5-750 and the Core i7-860). It’s a refinement of the Nehalem microarchitecture first revealed in the Core i7-900 series CPUs.

Like its stablemates, the i7-870 combines four CPU cores on one 45nm die, with on-chip memory and PCI bus controllers. The 8MB of shared L3 cache remains too. Like all Core i7 chips it features Hyper-Threading, which lets it work as a virtual eight-core CPU. And rather than the LGA 1366 format of the older Core i7s, Lynnfield chips use the more petite new LGA 1156 socket.

The most exciting development is Turbo Mode, which borrows power from idle CPU cores to overclock active threads. This was introduced with the first Core i7 CPUs, but those parts could boost a single thread only by a maximum of 266MHz, whereas Lynnfield can raise the speed of a single core by as much as 667MHz – a significant enhancement.

Performance

The i7-870’s model number suggests it’s a lesser part than the old 900-series Core i7s, and its 2.93GHz clock speed (disregarding Turbo Mode) is only on a par with the old Core i7-940. Yet in our real-world benchmarks it proved an impressive performer.

When tested in a Gigabyte P55 motherboard with 2GB of DDR3-1066 RAM, an ATI Radeon HD 4550 graphics card and a Seagate Barracuda 7200.12 hard disk, it achieved 2.03 – ahead of the older Core i7-940, which scored 1.98 in a similar configuration. This was, however, still some way behind the 3.2GHz Core i7-965, which reached 3.2GHz at stock speeds and which, being an “Extreme Edition”, can easily be turned up even higher.

Still, thermal design power for the Core i7-870 is quoted at a comparatively low 95W, and our test system idled at a mere 60W. Even when we drove all four cores up to full load, total power draw peaked at just 124W. Some older Core i7 systems draw that much when idle.

Price

The big problem with the Core i7-870 is cost, with early online prices coming in at £382 exc VAT. That’s hard to justify when AMD’s Phenom II X4 965 delivers similar performance for less than half the price.

On that basis, it’s very hard to recommend this particular model. It could perhaps be a decent choice for a hardcore workstation PC – but then those who are willing to pay for top-notch performance will do better with the Core i7-965. Though Lynnfield is unarguably a technical achievement, it’s hard to imagine a question to which an i7-870 is the best answer.

Specifications
Cores (number of)	4
Frequency	2.93GHz
L2 cache size (total)	1.0MB
L3 cache size (total)	8MB
FSB frequency	N/A
QPI speed	N/A
Thermal design power	95W
Fab process	45nm
Virtualisation features	yes
HyperTransport frequency	N/A
Clock-unlocked?	no
Performance tests
Overall application benchmark score	2.03