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Intel Atom vs Xeon performance

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I recently got myself a small laptop, an Asus Transformer Book T100TA, and I'm surprisingly happy with it. The current …

I recently got myself a small laptop, an Asus Transformer Book T100TA, and I'm surprisingly happy with it. The current generation of these devices is what netbooks were supposed to be: very portable, with a very long battery life, but still powerful enough to be usable. In fact, I'm writing this blog post on it. Finally, both the hardware and the software (the device is running Windows 8.1 and I'd be crazy to replace it with anything else) have caught up with the idea. I honestly recommend this device if you bought a netbook back in the day and were disappointed with its general quality and usability.

Anyway, I'd like to talk about something else: the performance of the CPU in this device. My edition of the T100TA is equipped with a quad-core Intel Atom Z3775 nominally clocked at 1.46 GHz, but spanning from 0.53 GHz to 2.39 GHz (with turbo boost). It also eats up around 2 W of electricity at the nominal frequency. This is the currently newest model of the Atom CPU, and has four "proper" cores, instead of two + hyperthreading like the preceding editions. I was so surprised about its performance in daily use that I simply had to compare it to my (very) old desktop machine. This machine was very sleek back in the day, with a Xeon E5405 CPU at 2 GHz (this model is fixed-frequency). Both machines are running Windows (though the older one runs Windows 7), I've used the openssl's speed benchmark and exactly the same cygwin binaries.

Update: By popular request, I have added a benchmark of a modern, state of the art low-mid-range Xeon CPU, the E3-1230 v3. Note that this CPU works on a significantly faster frequency, is attached to much faster RAM, and the benchmark was done with a modern Linux's OpenSSL (1.0.1) instead of an older version (0.9.8) on Windows.

CPU Xeon E3-1230 v3 Xeon E5405 Atom Z3775
Norm. freq. 3.3 GHz 2 GHz 1.46 GHz
Turbo. freq. 3.7 GHz 2 GHz 2.39 GHz
RAM freq. DDR3-1600 FBDIMM-800 DDR3-1066
RC4 865 MB/s 213 MB/s 212 MB/s
SHA256 275 MB/s 60 MB/s 43 MB/s
AES-128-CBC 164 MB/s 106 MB/s 94 MB/s
RSA2048 987 s, 31090 v 73 s, 2906 v 36 s, 1303 v

The results reported above are for the single-core version of the benchmark, and for the 1k block size for the AES, SHA256 and RC4 algorithms. AES was not hardware-accelerated.

So there you go, the Atom CPU from 2014 has the performance directly comparable to that of a full-blooded Xeon from 2007. By the time this Xeon CPU gets to be 10 years old, it will surely be surpassed by the new Atoms.

This result in cryptography also means that a relatively low-end Atom CPU such as this one (and there are more powerful server editions available) can easily saturate a gigabit link with SSL/TLS-protected traffic, at least for non-dynamic content.

Now consider what this means for the power usage: both Xeons draw 80 W, while the Atom draws 2 W.

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