Broadwell Linux Ultrabook Running MUCH Cooler Than Haswell
Written by Michael Larabel in Intel on 25 January 2015 at 02:44 PM EST. 18 Comments
Aside from the performance benefits of Broadwell, particularly in having greater graphics capabilities, laptops and ultrabook designs are much more power efficient than former Haswell products. Here's some quick tests I did today comparing the Broadwell-based Core i7 ThinkPad X1 Carbon to my former Haswell-based Core i7 ASUS Zenbook ultrabook.

My formal X1 Carbon benchmarks comparing this newest Lenovo ThinkPad model to various laptops/ultrabooks atop the same software stack will come in short order, but I did run some benchmarks today comparing the X1 Carbon to some old thermal results I had for the ASUS Zenbook UX301LA. While initially that Zenbook was great and has served as my main production system, its ran into thermal issues to the point I no longer fully max out all CPU cores on the system with fear of the system locking up or randomly rebooting. In fact, under normal reboot, sometimes there's still random reboots without notice.

That Zenbook is equipped with an Intel Core i7 4558U Haswell processor, 8GB of RAM, dual 128GB SSDs, and Intel Haswell Iris graphics. I had some thermal results of the Zenbook from when it was brand new so I've seen how the new X1 Carbon compares directly to this old data. As mentioned already, a proper comparison when the Zenbook and other laptops/ultrabooks I have around will be compared directly in a future multi-page comparison article. To recap, my X1 Carbon specs, it has a Core i7 5600U Broadwell processor, HD Graphics 5500, 8GB DDR3 memory, and 128GB Samsung SSD.

As this was a rudimentary comparison going against old results, there are the obvious software differences but that will be addressed in the large articles with proper tests, but for means of comparing the CPU temperatures it's fine especially with both ultrabooks using the Intel P-State CPU scaling driver with powersave governor.

Running the same Xonotic build and settings on each ultrabook showed the Broadwell X1 Carbon being much cooler than the Haswell Zenbook. Over 30C cooler!

The Haswell Core i7 4558U is a dual-core part with Hyper Threading that has a base clock speed of 2.8GHz and a turbo frequency of 3.3GHz. The TDP of this 22nm mobile CPU is 28 Watts. The i7-5600U meanwhile is also a dual-core part with Hyper Threading but has a 2.6GHz base frequency and a 3.2GHz turbo frequency. However, this 14nm Broadwell processor has a TDP of just 7.5 Watts!

This Broadwell CPU has close to the same clock frequencies yet consumes just a quarter of the power of the Haswell CPU it's being compared to.

When running CPU-bound tests, the Broadwell X1 Carbon results also continued showing a magnificent difference... This X1 Carbon doesn't get hot when it's on my lap and enduring these demanding Phoronix Test Suite tests.

When building the Linux kernel across all CPU cores, the Broadwell ThinkPad was almost 30C cooler. The X1 Carbon also emits no real noise.

At least I shouldn't be running into any thermal problems with the Lenovo ThinkPad X1 Carbon thanks to the Broadwell CPU!

While there's the software stack difference with Ubuntu 14.04 vs. 15.04, if you want to see the basic performance metrics before waiting for my proper results, visit this result file page. Again, if you appreciate all of this Linux hardware testing done at Phoronix over the past eleven years by yours truly, please consider subscribing to Phoronix Premium or making a PayPal tip to help cover these hardware expenses, the time to do this testing, etc. Thanks!

If you missed it yesterday were also my Broadwell: Windows vs. Linux OpenGL results from this X1 Carbon.
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Michael Larabel is the principal author of and founded the site in 2004 with a focus on enriching the Linux hardware experience. Michael has written more than 20,000 articles covering the state of Linux hardware support, Linux performance, graphics drivers, and other topics. Michael is also the lead developer of the Phoronix Test Suite, Phoromatic, and automated benchmarking software. He can be followed via Twitter or contacted via

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