Broadwell vs. Haswell – Duel of the ULV Processors

First, let's have a general view of the product range: Alike in Haswell, Intel categorizes the Broadwell CPUs in the Core i3, Core i5, Core i7 series (we ignore the Pentium and Celeron series here) depending on price, performance, and feature set. While all models feature Hyper-Threading, which allows parallel processing of four threads, only the more expensive Core i5 and Core i7 models have a CPU Turbo. In addition, the high-end Core i7 series boasts a bigger L3 cache, which does not have a big impact on performance, though.

If you compare certain Broadwell and Haswell models directly, the significantly higher base clock is striking. Thanks to the 14 nm process Broadwell chips require less energy at the same clock rate. The TDP, which remained 15 Watt in the ULV class, less often limits the clock rate. This can also be seen in the dual-core Turbo, which increased by 100 to 200 MHz in many models. It is interesting that it is the other way round for the one-core Turbo. Likely, the manufacturer uses slightly lower frequencies than previously for efficiency reasons.

CPU Performance

Apart from per-MHz performance, which is about 5% higher in Broadwell, two questions are particularly interesting for the performance in the following CPU benchmarks: What is the maximum Turbo clock? How high can the clock rate be so that the power consumption remains just under 15 Watt?

It is important to differentiate this since it takes about 30 seconds until the TDP restriction kicks in - ULV chips are also allowed to take 20 Watt and more for a short time. Thus, the maximum Turbo has an impact on how well the CPU copes with short load peaks, while the answer to the second question gives information about the permanently available performance. Cinebench example (Multi): Depending on the quality of the chip, Haswell processors have to reduce the clock rate to about 2.6 GHz at the end of the test, while Broadwell keep clocking at about 2.8 GHz in the same scenario (provided the Turbo Boost scope of a particular notebook allows such frequencies at all). The TDP problem does not influence single-thread benchmarks, since even the power consumption of the fastest models remains under 15 Watt, anyway.

As a result, the high-clocked Broadwell models perform especially well in long-lasting tests with full load on both cores. Apart from Cinebench this is, for example, also true for our x264 benchmark. On average, the new i7-5600U top model is just under 13% faster than the i7-4600U. The difference between the i7-5200U and i5-4200U is similarly big, while the i5-5300U only outperforms the i5-4300U by about 9%. In contrast, the single-thread performance remained almost the same. Increases of above 5% are exceptions in all pairings.

You could call the Core i3-5005U the secret star of the complete line-up: With 2.0 GHz it clocks 300 MHz higher than the old Core i3-4005U, which leads to a notable performance gain of significantly above 20%.

Verdict: In terms of CPU, the Core i3 models of the Broadwell generation are particularly attractive since their relative performance gain compared to Haswell is highest. In view of the price-performance ratio, the Core i5-5200U strikes a reasonable balance.

GPU Performance

Just like Haswell ULV processors, Broadwell ULV processors also come with three different graphics solutions: a low-end model for Celeron and Pentium models (GT1, 12 EUs), a standard model for the Core series (GT2, 24 EUs) and a high-end model for selected i5 and i7 models (GT3, 48 EUs). So far, we could only test the mid-range GT2 model, HD Graphics 5500, in detail, which features exactly 20% more shader units than the older HD Graphics 4400 (20 EUs). In addition, Intel applied many changes to the architecture and slightly decreased the clock rates, which makes a theoretical estimation of the performance more difficult.

However, meaningful benchmarks of integrated graphics units also have their pitfalls in practice: processor performance, L3 cache, RAM connection and throttling can have a big impact on the results. Therefore, we tried to select as many devices and benchmarks as possible to get a representative impression.

With the same RAM configuration, the HD Graphics 5500 is just under 20% faster than the HD Graphics 4400. Since the difference between single and dual-channel connection alone affects performance by about 20 to 25%, an HD 5500 with only one RAM module cannot completely reach the performance of an HD 4400 with two DIMMs. In view of the long development period, the GPU is a little disappointing. In 2013, Haswell came closer to dedicated low-end solutions than Broadwell today.

Verdict: The RAM connection has a much bigger impact on performance than the processor model. Maximum frame rates are only possible with fast dual-channel RAM. The absolute performance is modest in any case: Even a GeForce 820M proves to be faster in many cases.