Alienware M11x R2: A Legend Rebornby Jarred Walton on July 9, 2010 4:05 AM EST
Overclocked Performance: Win Some, Lose Some
Like the M11x and ASUS' UL series of CULV laptops, the M11x R2 allows you to try overclocking the CPU via the BIOS. Whereas we could simply set the bus speed to 166MHz (from the default 133) with the other laptops we've tested, this is our first Arrandale ULV processor and it didn't quite make it to a 166 bus. At 166, the system would reboot twice and revert to 133. A 164MHz bus on the other hand would boot Windows most of the time, but various games and applications would crash. Eventually we settled on 160MHz and achieved full stability.
Note that the stock multiplier for the i7-640UM is 9x, but with Turbo Boost it can go as high as 17x. You can disable Turbo Boost in the BIOS, but even at a 166 bus speed you would then be stuck with a constant CPU clock of only 1500MHz. At 160MHz we still saw multipliers as high as 17x, but not as often as when we were on the stock 133MHz bus. What's more, in heavily threaded benchmarks the multipliers were much lower on average, with the system often running at the "minimum" 9x. (SpeedStep can still drop down to a 5x multiplier, but under load we always stayed above 9x.)
So, what does overclocking get you? In certain situations we got much better performance, but overall it wasn't worth the effort in our opinion. Here's a table of our results.
M11x R2 Overclocking Gains - Applications
160MHz Base Bus
|3DMark Vantage (Entry)||14441||14484||100%|
|x264 Pass 1||29.72||29.23||98%|
|x264 Pass 2||7.68||7.23||94%|
The workloads that are primarily single-threaded in nature showed the biggest improvements. 3DMark03/05 both increased, with Peacekeeper and the single-threaded Cinebench result showing the greatest benefit. Most of the remaining tests showed no benefit, and in the case of heavily threaded tasks the bus overclock actually reduced performance. So from a general application standpoint, we can't see a reason to bother with the overclock; let Intel's Turbo Boost do its thing and be happy. But then, this is a gaming laptop and games are sometimes more single-threaded in nature. Can any games benefit from overclocking?
M11x R2 Overclocking Gains - Gaming
160MHz Base Bus
|Game Title||Stock||160 Bus||Percentage|
|Batman: Arkham Asylum (Very High)||63||62||98%|
|Battlefield: Bad Company 2 (Medium)||31.6||32.1||102%|
|Crysis: Warhead (Mainstream)||32.5||36||111%|
|DiRT 2 (Medium)||34.8||36.1||104%|
|Empire: Total War (Medium)||51||51.4||101%|
|Far Cry 2 (Medium DX9)||38||40.7||107%|
|Left 4 Dead 2 (Very High)||43.2||43.4||100%|
|Mass Effect 2 (Max)||37.2||38.6||104%|
|STALKER: Call of Pripyat (Med. + Full Dyn.)||57.5||61.6||107%|
In general, the answer is no, though we do see minor improvements of 4-7% in several titles. The biggest increase was Crysis: Warhead at 11%, but even there the difference will be difficult to notice without benchmarks.
Overall, overclocking turned out to be of little use, but we do have one final disclaimer. We're using the i7-640UM processor, which runs at 1.20GHz to a maximum Turbo speed of 2.27GHz. It's possible that the i5-520UM with its lower speed range of 1.07GHz to 1.87GHz might benefit more, but without testing we can't say for sure. We do know that on an ASUS Core i7-720QM notebook our results were similar—overclocking caused Turbo Modes to kick in less, resulting in generally lower performance—so while you can get some impressive overclocks out of i5/i7 desktop processors, in a notebook you're likely best off just going with the stock speed and Turbo Boost.