Intel Core i5-750 review

Intel has launched its Core i5 processor, previously known the codename Lynnfield. The first chip is the Core i5-750, a quad-core processor running at 2.66GHz. Intel is aiming the Core-i5 at users who want excellent performance but aren't willing to pay the high prices demanded by current Core i7 PCs.

It wasn't that the original Core i7 processors were unreasonably priced, given their incredible computing power, but the cost of compatible motherboards, and triple-channel DDR3 memory kits, made for expensive systems.

Core i5 may share branding with the existing Core i7 chips, but it has a very different architecture and uses an entirely new processor socket, called LGA1156, which requires the new Intel P55 motherboard chipset. The new socket means Core i5 processors won't be compatible with current Core i7 motherboards using the LGA1366 socket. Confusingly, there are also new Core i7-branded Lynnfield processors being launched, which will also use LGA1156. We find it disappointing that Intel, a company that has stuck by its LGA775 socket since 2004, has now introduced two new designs in such a short space of time.

The new processor architecture means there's no need for a Northbridge chip on the motherboard. This is largely thanks to a built-in memory controller, which has support for dual-channel DDR3 modules at speeds of up to 1333MHz - although you can boost memory speeds further by overclocking the processor's FSB above its usual 133MHz. There's also a dedicated link with your PCI-Express graphics card or cards. Although P55 boards are, thankfully cheaper than their X58 predecessors, they're still twice the price of equivalent AMD boards.

We were surprised to find official support for overclocking in the form of Intel's new Turbo Boost technology. When the processor comes under load, this increases the multiplier beyond its usual 20x setting. Intel claims the Core i5-750 will go up to a 24x multiplier, running at a speed of 3.2GHz. This is dependent upon having both a capable power supply and sufficient cooling. You won't receive the full boost on every core simultaneously. We saw speeds of 2.93GHz on all four cores in multi-threaded tasks, like our Video-encoding test, but it only hit 3.2GHz in single-threaded tasks, like some games and our Image-editing test.

We found Turbo Boost support to be rather hit and miss. Two of the P55 boards we tested our processor sample on refused to budge over 2.8GHz. We can only assume that BIOS support for this feature hasn't been fully implemented; in fact there was no mention of it at all on one board. Thankfully, a third attempt on Gigabyte's P55M-UD4, opposite, worked perfectly, hitting the maximum clock speed in our Image-editing test and completing the task 44 per cent quicker than our AMD Phenom II reference PC.

The Core i5-750 was no slouch in any of our benchmarks, scoring a stunning 136 overall. This is considerably quicker than the fastest of AMD's Phenom II chips, the X4 965, and only just behind the slowest of Intel's original Core i7 chips, the 920. This is very impressive for a processor that costs around £20 less than the X4 965, and around £40 less than the Core i7-920.

Its fast application scores are partly thanks to a large, three-stage memory cache, which provides a smooth flow of data to the processing cores. There's 64KB of L1 and 256KB of L2 cache per core and then a shared 8MB of L3 cache - 2MB more than recent Core 2 Quad chips. The largely-identical Lynnfield Core-i7's will have Hyper-Threading, so Windows sees them as having eight cores, but Intel has disabled it in the Core i5 chips. Despite this, a score of 135 in our Video-encoding test shows it's still lightning-quick when it comes to multithreaded applications.