The Core i7 CPUs

Intel is offering three Core i7 SKUs at launch: the flagship Core i7 965 Extreme Edition clocked at 3.2GHz, the midrange Core i7 940 running at 2.93GHz, and the entry-level Core i7 920 which runs at 2.66GHz:

Intel Nehalem SKUs
Processor	Core i7-965 Extreme Edition	Core i7-940	Core i7-920
Clock Speed	3.20GHz	2.93GHz	2.66GHz
QPI Speed	6.4 Gigatransfers/sec	4.8 Gigatransfers/sec	4.8 Gigatransfers/sec
L3 Cache Size	8MB	8MB	8MB
Unlocked Clock Multiplier	Yes	No	No
Memory Speed Support	DDR3-1066	DDR3-1066	DDR3-1066
TDP	130W	130W	130W
Price	$999	$562	$284

Nehalem is built on Intel’s 45-nm manufacturing process high-K metal gate transistor technology with a die size of 233 square millimeters and approximately 731 million transistors. In comparison Penryn’s transistor count was 820M transistors and a 214mm2 die.

CPUs compared: Core i7 (left) and Core 2 Quad (right)

Core i7 (left) compared to Core 2 Quad (right)

Memory Compatibility

As some sites have mentioned ahead of the Nehalem launch, officially the CPU supports DDR3 memory rated up to 1.6V. According to Intel, memory running at voltages higher than 1.6V can potentially damage the CPU. Most memory manufacturers have announced their own triple-channel Nehalem-ready memory kits ahead of today’s launch, we recommend anyone interested in building their own Nehalem system go with one of these kits. Intel will be providing a list of certified memory modules on their developer website as well that you’ll want to check out before purchasing anything.

We opted to play it safe for now and stick with the stock memory voltage for all our Nehalem testing.

Motherboard Compatibility

Intel’s X58 chipset is the only platform that supports Core i7 at this time. X58 is Intel’s flagship chipset, with support for up to 36 PCIe lanes and supports PCIe 2.0. PCI Express Graphics solutions supported include 1x16, 2x16, and 4x8, with the chipset supporting ATI CrossFire and NVIDIA SLI (although as we’ve reported in the past motherboard manufacturers must submit their X58 boards to NVIDIA for proper SLI certification).

We’re going to try and do a dedicated SLI/CrossFire article around the end of this month.

The motherboard we used for our Core i7 testing is Intel’s own DX58 Smackover board. The Smackover board is a fairly nice board, with a good layout and enough features to please the mainstream user, although enthusiasts will probably want to opt for a higher-end motherboard from ASUS, EVGA, Gigabyte, or MSI with 6 DIMM slots and CrossFire/SLI support (Smackover doesn’t support SLI at this time).

The motherboard offers base clock speeds up to 240MHz (Nehalem’s stock base speed is 133MHz with the i7 920 relying on a multiplier of 20.0x (20.0x133=2660), the 940’s multiplier is 22.0x (22x133=2926) and the 965 has a multiplier of 24) in 1MHz increments. Memory multipliers of 6.0 and 8.0 are also selectable in BIOS (6.0x133=800MHz DDR3, 8.0x133=1066MHz DDR3), as well as a 10.0x (1333MHz DDR3) and 12.0x (1600MHz DDR3). The latter two multipliers were only selectable for our Extreme Edition CPU however.

In terms of voltages, the board provides CPU voltage settings up to 1.6V in 0.0125V increments, chipset voltages up to 1.50V (0.025V increments) and voltages for the QuickPath Interconnect up to 1.8V (0.025V increments). Memory voltage settings up to 2.5V are available in increments of 0.04V. The QPI data rate is also adjustable.

Overclocking

We were pleasantly surprised with how far we were able to push our Core i7 processors. The Core i7-920 managed to hit speeds of 3.6GHz (20.0 multiplier x 180MHz host bus) and 1.4875V of juice, with the chip pushing 3.9GHz thanks to Turbo Mode. At stock voltage the chip maxed out at 3.1GHz (20x155MHz bus).

We were actually able to run the system at even higher speeds within Windows, but the system wasn’t 100% stable at higher speeds and the occasional Windows crash. With more voltage we’re pretty sure we could’ve got the PC to run stable, but we weren’t willing to crank the voltage up beyond 1.5V with our shiny new Core i7 processor.

The Core i7-965 EE topped out even further, hitting speeds of 4.08GHz (30.0 x 136) with 100% stability. Once again we needed 1.4875V to get everything running stable, although in this chip’s case we’re pretty confident we hit the ceiling of its capabilities. At any higher speeds Windows failed to load.

To cool the processor, we used a Thermalright Ultra-120 eXtreme RT for all our OC attempts.