Lenovo ThinkPad X240 Ultrabook Review: A Philosophical Shift
Performance - Introduction, Processor, Application Performance
The X240 features the same CPU as the T440s we reviewed before it, and in fact, apart from a larger (double capacity) SSD and 8 GB RAM (versus the T440s’ 4 GB, both single-channel), it’s nearly identical in terms of configuration. As such, we should expect to see very similar overall system performance in our synthetic benchmarks, excluding ones which directly correlate with those areas of discrepancy (i.e., storage benchmarks and those heavily dependent on GPU memory).
In terms of comparisons to other models, the two most obvious candidates would be the T440s and the X230 we reviewed a year ago. Both provide interesting context, as the T440s is so similar in overall configuration, and the X230 is the last X series machine to date with full-voltage components. Our benchmarks will answer the question of just how much performance we’ve sacrificed in the switch to a ULV chipset, as well as how that translates to power conservation—and ultimately, whether it was worth it.
Before we get to the actual benchmarks, let’s take a look at how the system handles stress. Under full CPU load (using FurMark’s CPU Burner component), we recorded a maximum system temperature (after 30 minutes of stress) of 77°C, while the CPU held its frequency at a stable 2.3 GHz (the maximum Turbo Boost for two-core operation). That’s encouraging, as it means that CPU-intensive tasks should be no trouble for the X240.
In precisely the same way as the T440s (and even the Flex 14 before it), however, the instant any significant degree of GPU load is introduced, the machine immediately throttles both CPU and GPU. The maximum internal temperature was 74.1°C, but the GPU only managed to reach 700 MHz consistently. The CPU, on the other hand, dropped its clock rate to around 900–1000 MHz, which is—again—the same thing we saw with the T440s. The biggest difference here is that the internal temperature is around 8°C warmer than the max temperature we recorded during stress with the T440s (nevertheless, both machines throttle in nearly identical fashion). As we expected, our final test of combined GPU and CPU stress also provided identical results, with the CPU throttling to 800–900 MHz and the GPU reaching just 600 MHz.
Performance – Processor
The X240’s Intel Core i5-4200U CPU is the same as that in the T440s we reviewed. This is a 1.6 GHz Haswell ULV model that can Turbo Boost up to 2.6 GHz (2.3 GHz for two active cores). Meanwhile, unlike the X230’s 35W TDP CPUs, the i5-4200U features a low TDP of just 15 W.
SiSoft Sandra Processor Benchmark
Here we have our first example of how the TDP affects the overall CPU performance. Our results from SiSoft Sandra are nearly identical to the T440s and the Flex 14, and even very similar to that of the ThinkPad Twist (which featured an Intel Core i5-3317U). As we noted in our T440s review, the X230’s results are far an above those of the X240 thanks to its more powerful (and more power-hungry) CPU: in this case, it’s 33% and 48% higher than the X240 in Whetstone and Dhrystone, respectively. That’s a significant margin if you’re planning on any sort of CPU-heavy activity.
Although both units beat the Flex 14 on OpenGL performance (likely due to a difference in driver versions), the X240 and the T440s are essentially neck-and-neck in the Cinebench tests.
Since Peacekeeper cares as much about the browser as it does the actual hardware, it’s worth always taking its results with a grain of salt. Still, the X240’s total score of 2585 is right in line with the T440s and a little above the Flex 14.
CPU benchmarks notwithstanding, let’s see how well the X240 fares in terms of general performance.
PCMark 7 is always our first reference in this regard, and though it heavily favors machines with an SSD, that’s not necessarily a bad thing, as machines with SSDs really do feel that much faster than most which lack that trait. Here, the X240 scores nearly identically to both the T440s and the Flex 14, which seems to suggest that (since the T440s and Flex 14 share the same oddly subpar SSD), the benefits of a fast storage device eventually diminish beyond recognition in the benchmark’s eyes. We’re also content not to argue with that interpretation, as to be honest, we can’t tell much of a performance difference between any of the three machines. That is to say, they all feel fast.