Intel's fifth-generation Broadwell CPU has been the default laptop processor of choice since its debut in January, but it's been difficult to get a real read on just how much of an improvement it really was over its Haswell predecessor.
That's because unlike desktops, where it's easy to control the environment they run in, laptops are complete packages. I tried to compare the updated ThinkPad Carbon X1 Carbon with Broadwell to the Haswell ThinkPad Carbon X1, for instance, but it wasn't quite apples-to-apples. I initially determined that the Broadwell CPU was significantly faster than the Haswell. Something didn't ring right, though, and ultimately I decided Lenovo's redesign of the laptop likely contributed to the results and really made it useless to try to draw any conclusion on the CPUs themselves.
My second chance came when I found upon two laptops that were identical--save for the CPU. Dell's commercial Latitude E5250 at one point simultaneously shipped with Haswell and Broadwell parts.
The chips are very close. The Haswell-based E5250 uses an Intel Core i5-4310U, a dual-core chip with Hyper-Threading and a rated clock speed from 2GHz to 3GHz. The Broadwell-based E5250 has a Core i5-5200U that's also a dual-core with Hyper-Threading and ranges from 2.2GHz to 2.7GHz. While the Broadwell's base clock speed is a little higher, its top speed is a bit lower. Perhaps more importantly, both CPUs are also the same price.
For graphics, the Broadwell has Intel HD 5500, while the Haswell has Intel HD 4400 graphics. If you want to see more details of the two CPU competitors, I've lined them up right here at Intel's ARK site.
Everything else, from what I can tell, is the same. Both feature touch-panel, 1920x1080-resolution displays, 256GB Samsung mSATA PM851 mSATA drives, 8GB of DDR3L RAM in single-channel mode, the same 51-watt-hour capacity batteries, and the same Windows 8.1 OS. In fact, both even use the same motherboard, which I visually confirmed by opening up both E5250 laptops. The only difference in the motherboard is one has a Haswell soldered down to it, while the other has a Broadwell soldered down to it. This is no surprise: Intel designed the Broadwell to be "drop-in" compatible, and many makers did just that.
For benchmarks, I stuck with tests that would isolate the CPU performance as much as possible. First up is the pure CPU benchmark Cinebench R15, which measures a chip's performance rendering 3D. The performance, for the most part, is very close--but surprise, the Haswell chip actually wins here. I suspect that's because the single-threaded mode gives the Haswell chip a small advantage due to its higher clock speed when on Turbo Boost mode. The Broadwell tops out at 2.7GHz vs. the 3GHz of the Haswell chip's top speed. That gives the Haswell chip about a 10-percent clock speed advantage.
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