X-Gene 1, Atom C2000 and Xeon E3: Exploring the Scale-Out Server World

Quick Overview of the SoCs

In this review, we compare four different SoCs:

• Intel's Xeon E3-1240 v3 3.4GHz
• Intel's Xeon E3-1230L v3 1.8GHz
• Intel's Xeon E3-1265L v2 2.5GHz
• Intel's Atom C2750 2.4GHz
• AppliedMicro's X-Gene 1 2.4GHz

We have discussed the Xeon E3-1200 v3, Atom C2000, and X-Gene in more detail in our previous article. What follows is a quick discussion of why we tested these specific SKUs.

The Intel Xeon E3-1240 v3 is a speedy (3.4GHz, eight threads) Xeon E3 that is still affordable and has a decent TDP (69W). If you want a 6% higher clock (3.6GHz), Intel charges you 2.3X more. The Xeon E3-1240 v3 has an excellent performance per dollar ratio.

The Xeon E3-1230L v3 paper specs are incredible: eight cores that can boost to up to 2.8GHz (with a base clock of 1.8GHz) and a very low TDP of 25W. To see how much progress Intel has made, we compare it with the 45W Intel E3-1265L v2 at 2.5GHz based on the Ivy Bridge core. Will the Haswell core be enough to overcome the 700MHz (1.8 vs 2.5GHz) lower clock speed, which is necessary to make the chip work with a very low 25W TDP? How does this very low power Xeon with the brawny core compare to the Atom C2750?

The Atom C2750 is Intel's fastest Atom-based Xeon. We are very curious to see if there are applications where the eight lean cores can outperform the four wide cores of the Xeon E3.

And last but not least, the X-Gene 2.4GHz, the first server SoC incarnation of the ARMv8-A or AArch64 instruction set. The X-Gene has twice as many memory channels and can support twice as many DIMM slots as its Intel competitors. The cache architecture is a mix of the Atom C2000 and Xeon E3. Just like the Atom, two cores share a smaller L2 cache (256KB vs 1MB). And like the Xeon E3 (and unlike the Atom C2000), the X-Gene also has access to and 8MB L3 cache. Less positive is the antiquated 40nm production process and the fact that power management is much less sophisticated than Intel's solutions. The result is a relatively high 40W TDP.

While not every application was available on the X-Gene, we gathered enough datapoints to do a meaningful comparison. Where will the first productized ARMv8 chip land? Will it be an Atom C2000 or Xeon E3 killer, or neither? What kind of applications run well, and what kind of applications are still running much faster on a x86 chip?

We've added a few CPUs/SoCs to further improve the comparison. We've thrown in the Atom N2800 to mimic one of the worst Intel server CPUs ever (well, maybe "Paxville MP" was worse), the Atom S1260. The Xeon X5470 ("Harpertown", Penryn architecture) is also featured just to satisfy our curiosity and show how much performance has evolved. To understand the performance of the different SoCs, we should also take into account that the Intel chips almost always run at a higher clock speed than the advertised clock speed, thanks to Turbo Boost.

The 1.8GHz clock of the 25W TDP Xeon E3-1230L v3 may seem pretty low, but in reality the chip clocks at 2.3GHz and more. Single-threaded performance is even better with a top speed of 2.8GHz. The same is true for the Xeon E3-1265L v2, which has an even greater delta between the advertised clock speed (2.5GHz) and the actual clock speed (3.1 – 3.4GHz) when we run our benchmarks.