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Mobile performance – a look back

[1]How fast are mobile CPUs [2] these days? Well, they are pretty fast processors.

While some still consider that x86 is ten times faster than ARM [3], that is just not the case anymore these days, the difference is much smaller, and closer to just two times if you compare a regular smartphone to a regular laptop/desktop.

CPU JavaScript Performance x86 vs ARM

The difference between the ARM [4]-powered low-cost Samsung Chromebook [5] and the high-end x86 [6]-powered Chromebook Pixel [5] is usually around or less than two times [7]:

Benchmark ARM Samsung 550 Chromebook x86 Pixel Chromebook How much faster?
SunSpider [8] 776 480 1.6
Octane [9] 5585 11846 2.1
Peacekeeper [10] 2142 3753 1.7
Kraken [11] 2265 4962 2.2
RoboHornet [12] 80.6 120.7 1.5

Those were JavaScript benchmarks, but this was pitting a Core i3 [13] processor. What about Atom [14], the low-power x86 offering? Anandtech [15] looked at it in their December 2012 x86 Atom review [16].

If you want x86 to pull further ahead, you need to use the power-hungry Core i7 [17], but the performance ratio still will not be ten times. On the other hand, the power consumption ratio might be closer to 100 times: a high-end Core i7 has a TDP up to 130W and really needs it [18], while the quad-core Krait [19] draws around 1-2 W under load [20] for a 4W TDP.

CPU floating-point performance

pi-black [21]I picked another computing benchmark, SuperPI [22]. This is a single-threaded benchmark, but it has historical results available from long ago. I’ve summarized a few scores:

Also keep in mind that quad-core is commonplace these days, five years ago, dual-core was the standard, ten years ago, it was single core everywhere but in very expensive servers. So there is an extra 4x ratio between old CPUs and modern ones.

Next: CPU and GPU in perspective. [24]

Previous: JavaScript and Floating Point. [25]

Mobile CPU performance in perspective

So we can summarize that a modern ARM smartphone or tablet has:

excel97 [26]And to put things in perspective, fifteen years old is the late 90’s, Excel and Word were at version 97, and very capable. Ten years old means Windows XP [27], Office XP and Microsoft Office dominance was complete.

You may also be surprised by the power difference between ten and fifteen years old PCs, well back then frequencies where still ramping up fast. We went from hundreds of MHz to the GHz range, and at the same time, CPUs became more efficient every year, requiring less clock cycles to achieve the same tasks, thanks to improved pipelining, out of order and speculative execution, specialized instructions, etc.

The rate of improvement drastically slowed once the GHz barrier was reached.

Mobile graphics performance

gf_fx_chip [28]The GPU [29] is the only area where desktop retains a significant lead, though maybe not as much as you think, see Anandtech’s comparison [30], the effective lead between a Surface Pro (x86) and an iPad 4 (ARM) is about 3x.

But once you look at things in perspective, modern GPUs support very complex pixel and vertex shading capabilities that their older brethren, so comparison with older hardware is not entirely fair.

There is a similar story that can be told about RAM: a Nexus 4 has 2GB of RAM, a modern regular desktop has 4GB. Two times ratio. Ten years ago, you could get along with 128 MB just fine, or 15 times less RAM than what the Nexus 4 has.