Review: We take Intel's fastest chip on the block for a serious spin, but the dent it leaves in our wallet is pretty huge.
We're still recovering from the overwhelming power of the Sandy Bridge microarchitecture, the successor to Nehalem in the 'low to midrange' arena. Even with all its might, the P67 Express Chipset has limitations with the amount of bandwidth available for memory, PCIe expansion cards, and other I/O compared to X58. The X58 Express chipset may have a bandwidth advantage, but the CPUs available for its accompanying 1366 pin socket are looking quite meek in comparison to the lesser 1155 pin socket.
Most enthusiasts opt for a single card in their system to avoid the oft-unreliable scaling of multiple card FPS. Those that take the plunge keep it at two cards, or purchase a dual core card such as the HD6990 or GTX 590. This is perfectly fine on the P67 platform. On the other hand, there's the minority who want the very best – quad SLI/Crossfire, triple channel memory, and enough cores to put small supercomputers to shame. And for this very purpose, Intel has introduced a very special beast – the Intel 990X.
While the popular (and affordable) Socket 1366 CPUs are fabricated on the 45nm node size, the newer 1155 processors bask in 32nm glory. The result is a significantly higher overclock ability on the latter, with lower voltages, heat output, and overall energy consumption. You may recall that the Intel i7 980X (another Extreme Edition part) was also fabricated on the 32nm process. The i7-990 is a direct evolution of this.
Six cores are contained within the familiar nickel/copper HIS , each with access to a 12MB pool of 'Smart Cache' (L3 cache) . The default clock rate has been increased from 3.33GHz to 3.46GHz (a mere multiplier increase from 25x to 26x) compared to the i7 980X, with the same fancy stock cooler which isn't particularly good (although spectacular compared to what you get with non-EE parts). Turbo mode is made available to boost the clock rate under load, up to 28x. Being an Extreme Edition CPU, this multiplier is unlocked, allowing us to go nuts when pushing this processor to its limits.
We didn't hesitate to drop the 990X into our test rig and ramp up the clocks. A 32x multiplier was our first port of call, which provided 4.256GHz of raw power to muck around with. That was quite stable at 1.35v without LLC, so we cranked up the multiplier a couple of notches where we managed a stable 4.522GHz with vcore bumped up to 1.4v.
Taking it a step higher required Level 1 LLC (on our new G1. Assassin motherboard) to maintain the 4.66GHz speed. This level of load line calibration reduced voltage discrepancies slightly, with vDroop reported by CPUz to be 1.36v. Level 2 LLC at this voltage produced 1.39v under load.
At this stage we wanted to try our hand at 5GHz, in order to match our menacing 2600K. To our dismay, we couldn't get it stable (we even tried 1.6v - shh don't tell!).
4.8GHz was our highest stable clock, albeit at an excessive 1.481v and Level 2 LLC. To put this into perspective, our previous runs with an i7 980X attained 4.4GHz (at a comfortable 1.41v, mind you).
It goes without saying, six cores at 4.8GHz and triple channel memory is one heck of a powerful set up. It's hot too, reaching 90c under load with our Noctua NH-D14 attached, yet amazingly cool at idle with temperatures reported at 28c.
The i7 990X blitzed PiFast, wPrime and CineBench multi-core tests. An interesting observation when compared to our previous 2600K runs is that a 5GHz Sandy Bridge processor edges ahead when it comes to single core tests. It goes to show, a CPU a quarter of the price can hold its own – now imagine if it had two extra cores!
While being an excellent performer, one must expect a lavish price tag to match the fact that this is a flagship chip. If one were to overclock the significantly cheaper i7 970, a clock rate of 4.2GHz is generally achievable. Assuming 4.8GHz is consistently achievable on the X990, what we get for double the price is 600MHz of headroom and an unlocked multiplier. For the asking price, that's a tough sell.
Issue: 137 | June, 2012