In the last few months you may have seen previews and news stories regarding Intel's new Core i7 desktop processor family, formerly known as Nehalem. Today, we're able to publish our impressions of Intel's new chip and ultimately its new platform. We've selected the flagship, $999 Core i7-965 Extreme Edition CPU to represent the Core i7 family, which at launch later this month will include three other processors, starting at $284. These new chips all require a new chipset, which will only exist at first by way of a very expensive new motherboard. We don't expect mainstream users will adopt Core i7 in any variation at first, at least until the motherboard prices come down. But the well-heeled performance hounds who do make the leap will enjoy the fastest consumer CPUs on the market.
Core i7 has enough architecture changes to require a brand new connection design between the chip and the motherboard. This is no small change, because Intel has stuck with the LGA775 (land grid array) chip socket since the days of Pentium 4. The new socket design, LGA1366, will not accept any older Intel CPUs, nor will Core i7 work on any older motherboards.
Unlike a new socket design, new chipsets aren't uncommon with updated Intel CPUs. The last three Extreme Edition chips Intel has launched each required its own new motherboard circuitry, and Core i7 is no different. Intel's new Core i7-supporting X58 chipset will only appear in very high-end boards. We conducted this review with the Intel Extreme Motherboard DX58SO board, and we've already reported on a new X58 board from Asus. Expect Gigabyte, MSI, and Intel's other typical board partners to introduce their own new X58 boards, and we expect prices will stay at or around the $300 mark. For this reason, Core i7 will remain an enthusiast CPU until Intel introduces a more moderate, mass consumption-friendly Core i7-compatible chipset.
Faster memory access
The reason for this platform shift has to do in part with a fundamental design change in Intel's CPU architecture. As has long been rumored, Intel has finally adopted an integrated memory controller into its Core i7 CPUs. What this means is that instead of the CPU communicating with a separate controller on the motherboard before it can talk to the system memory, Core i7 can save a step, and essentially receive data from the system RAM directly.
AMD adopted this integrated controller strategy in the early days of its Athlon dual-core processors, and it was one of the factors that led them to dominate the competing Intel Pentium D CPUs of that generation. Through superior design since then, Intel has regained its performance lead over AMD, and we suspect that by adding the on-chip memory controller to Core i7, Intel has only made it more difficult for AMD to find a design advantage moving forward.
A potential complication here is that the new memory controller has three channels to the RAM. That means that unlike most desktop setups, which involve two or four memory sticks, Core i7 systems will want memory sticks in multiples of three. Hence why Intel shipped our test system with only 3GB of RAM (we got creative with a 2x1GB, 1x2GB RAM configuration, for 4GB total for testing), and why in high-end PCs that use the new X58 platform, 3GB, 6GB, and 12GB configurations will be common. X58 will also only support DDR3 RAM, whose prices have thankfully come down over the past year.
Four cores, sometimes eight
If you've followed Intel's chips designs over the years, the term "Hyperthreading" shouldn't be unfamiliar. This technology lets Intel simulate more processing threads on top of its old dual-core Pentium 4 chips. It abandoned that strategy with the Core 2 family, but Intel has resurrected it with Core i7, and it's why you'll see eight processing threads when you bring up Windows' system performance screen. Few day-to-day programs will benefit from Hyperthreading, and it's more of a situational benefit for processing reliability and the scant few applications that can actually support so many threads. Core i7 will eventually hit eight native cores on a single CPU, or 16 processing streams with Hyperthreading, but Intel has not made it clear when that will happen. It may be worth the wait, if you know you'll need that much parallelism, but few consumers will.
Another significant change with the Core i7/X58 landscape had to do with graphics cards. Intel's Skulltrail platform of last year supported both standards as well, but the specialized CPUs that made the board worthwhile were prohibitively expensive. With the X58 chipset, yes, it comes on an expensive motherboard, but you can purchase a Core i7 chip to go with it for less than $300. The Core 2 Extreme QX9775 Skulltrail CPU started at $1,500. Gamers who stay current with graphics cards should be especially happy with this flexibility, as changing 3D card vendors will no longer require a wholesale system rebuild.
We tested both SLI and Crossfire setups on our Core i7 test bed and found both worked without trouble, requiring nothing more than installing the hardware and appropriate graphics-driver software as you would normally. As for their performance, AMD has issued a series of so-called "hot-fix" drivers to improve compatibility and frame rates of its cards with various PC games, which suggests that its software still needs to work out a few kinks on X58. Nvidia has not been shy to point out this fact (its beta drivers have worked fine), but we also find it telling that all three of the high-priced Core i7 gaming desktops we're currently reviewing come with multicard AMD configurations.
A quicker path
Finally, the last major change with Core i7 is the introduction of what Intel's calling the QuickPath Interconnect (QPI). Essentially this is the Intel version of AMD's HyperTransport interface between the CPU and the chipset. The major impact of the QPI for consumers is that Intel uses different QPI ratings to distinguish the Core i7-965 Extreme Edition from the non-Extreme Core i7 chips. Rated by Gigatransfers per second (Gigatransfers, or GT, refers to a million transfers of data), the Extreme Edition comes in at 6.4GT/sec, where the non-Extreme versions handle only 4.8GT/sec. In addition to that speed advantage, Intel also ships the Extreme version with an unlocked clock multiplier, which means it can be overclocked. The standard Core i7's will have to remain at their shipping speeds.
|Intel Core i7-965 Extreme Edition||Intel Core 2 Extreme QX9650|
|Manufacturing process||45 nanometer||45 nanometer|
|Transistors||731 million||820 million|
|L2 Cache||256kb/core||2 x 6MB|
|Front side bus||NA||1,333MHz|
|TDP||130 watts||130 watts|
To put the Core i7-965 Extreme Edition in perspective, we compared it with the year-old
|Rendering multiple CPUs||Rendering single CPU|
The Core i7 chip is faster than the QX9650 on every test, but we were most impressed by the CineBench multicore test and the Far Cry 2 benchmark, where Intel's new CPU established a sizable performance advantage. Gamers and digital-media editors may likely have assumed that Core i7 is worth their attention. As we can see from our testing, any such assumption is clearly justified.
We should add that the Core 2 Extreme QX9650 was actually surpassed earlier by the Core 2 Extreme QX9770, a $1,500 CPU that uses Intel's X48 chipset. Time constraints prevented us from testing that CPU as well, but based on early results from PC World Greece (via Engadget), it appears that Core i7 trounces that chip as well. We expect the Web will flood with reviews of the entire Core i7 family at the same time that this review launches. We encourage anyone considering a new CPU purchase to read as much coverage as possible to make the most informed buying decision. Any CPU with a $999 price tag merits careful consideration.
You'll note from our power-consumption tests that the Core i7 consumes almost the exact same amount of energy both at idle and while under load. We didn't expect major gains here, as each chip uses the same 45 nanometer process, runs at a similar clock speed, and with roughly the same number of transistors. Typically Intel gains power efficiency with chips introduced in a "tock" year, which involves a more efficient design of the chips from a "tick" year such as these. The Core i7-965 Extreme may have improved its relative power usage, in that it uses fewer transistors to do more work and at faster clock speeds than the older Core 2 Extreme chips. But anyone building a system with this new processor should expect to need an equivalently beefy power supply, especially if you intend to add multiple graphics cards and hard drives.
Find out more about how we test desktop systems.
Intel Core i7-956 Extreme Edition
Windows Vista Ultimate 64-bit; Intel DX58SO motherboard 4GB Kingston 1,066MHz DDR3 SDRAM; 1GB Nvidia GeForce GTX 280 graphics card; 74GB Western Digital 10,000 rpm hard drive
Intel Core 2 Extreme QX9650
Windows Vista Ultimate 64-bit; Asus Maximus Formula Special Edition motherboard; 4GB 800MHz DDR2 SDRAM; 1GB Nvidia GeForce GTX280; 74GB Western Digital 10,000 rpm hard drive