The IBM POWER8 Review: Challenging the Intel Xeon
by Johan De Gelas on November 6, 2015 8:00 AM EST- Posted in
- IT Computing
- CPUs
- Enterprise
- Enterprise CPUs
- IBM
- POWER
- POWER8
Energy and Pricing
Unfortunately, accurately and fairly comparing energy consumption at the system level between the S822L and other systems wasn't something we were able to do, as there were quite a few differences in the hardware configuration. For example, the IBM S822L had two SAS controllers and we had no idea how power hungry that chip under the copper heatsink was. Still there is no doubt that the dual CPU system is by far the most important power consumer when the server system is under load. In case of the IBM system, the Centaur chips will take their fair share too, but those chips are not optional. So we can only get a very rough idea how the power consumption compares.
| Xeon E5 299 v3/POWER8 Comparison (System) | ||
| Feature | 2x Xeon E5-2699v3 | 2x IBM POWER8 3.4 10c IBM S822L |
| Idle | 110-120W | 360-380W |
|
Running NAMD (FP) |
540-560W |
700-740W |
| Running 7-zip (Integer) |
300-350W |
780-800W |
The Haswell core was engineered for mobile use, and there is no denying that Intel's engineers are masters at saving power at low load.
The mightly POWER8 is cooled by a huge heatsink
IBM's POWER8 has pretty advanced power management, as besides p-states, power gating cores and the associated L3-cache should be possible. However, it seems that these features were not enabled out-of-the box for some reason as idle power was quite high. To be fair, we spent much more time on getting our software ported and tuned than on finding the optimal power settings. In the limited time we had with the machine, producing some decent benchmarking numbers was our top priority.
Also, the Centaur chips consume about 16W per chip (Typical, 20W TDP) and as we had 8 of them inside our S822L, those chips could easily be responsible for consuming around 100W.
Interestingly, the IBM POWER8 consumes more energy processing integers than floating point numbers. Which is the exact opposite of the Xeon, which consumes vastly more when crunching AVX/FP code.
Pricing
Though the cost of buying a system might be only "a drop in the bucket" in the total TCO picture in traditional IT departements running expensive ERP applications, it is an important factor for almost everybody else who buys Xeon systems. It is important to note that the list prices of IBM on their website are too high. It is a bad habit of a typical tier-one OEM.
Thankfully we managed to get some "real street prices", which are between 30% (one server) and 50% (many) lower. To that end we compared the price of the S822L with a discounted DELL R730 system. The list below is not complete, as we only show the cost of the most important components. The idea is to focus on the total system price and show which components contribute the most to the total system cost.
| Xeon E7v3/POWER8 Price Comparison | ||||
| Feature | Dell R730 | IBM S822L | ||
| Type | Price | Type | Price | |
| Chassis | R730 | N/A | S822L | N/A |
| Processor | 2x E5-2697 | $5000 | 2x POWER8 3.42 | $3000 |
| RAM | 8x 16GB DDR4 DIMM |
$2150 | 8x 16 GB CDIMM (DDR3) | $8000 |
| PSU | 2x 1100W | $500 | 2x 1400W | $1000 |
| Disks | SATA or SSD | Starting at $200 |
SAS HD/SSD | +/- $450 |
| Total system price (approx.) | $10k | $15k | ||
With more or less comparable specs, the S822L was about 50% more expensive. However, it was almost impossible to make an apples-to-apples comparison. The biggest "price issue" are the CDIMMs, which are almost 4 times as expensive as "normal" RDIMMs. CDIMMs offer more as they include an L4-cache and some extra features (such as a redundant memory chip for each 9 chips). For most typical current Xeon E5 customers, the cost issue will be important. For a few, the extra redundancy and higher bandwidth will be interesting. Less important, but still significant is the fact that IBM uses SAS disks, which increase the cost of the storage system, especially if you want lots of them.
This cost issue will be much less important on most third party POWER8 systems. Tyan's "Habanero" system for example integrates the Centaur chips on the motherboard, making the motherboard more expensive but you can use standard registered DDR3L RDIMMs, which are much cheaper. Meanwhile the POWER8 processor tends to be very reasonably priced, at around $1500. That is what Dell would charge for an Intel Xeon E5-2670 (12 cores at 2.3-2.6 GHz, 120W). So while Intel's Xeon are much more power efficient than the POWER8 chips, the latter tends to be quite a bit cheaper.
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Michael Bay - Saturday, November 7, 2015 - link
You are probably still hurry.Or just not civilized enough.
JohanAnandtech - Saturday, November 7, 2015 - link
I have to disagree with "only old legacy". One of things I really want to tackle is running Apache Spark on POWER. Spark is one of the most exciting Big Data tools, it is a very modern piece of software. IBM claims that the POWER8 is very good at it, and I want to check that.Jake Hamby - Friday, November 6, 2015 - link
Very interesting review! I've been a PowerPC fan for many years. I even bought a used PowerMac Quad G5 a few years ago to hack on FreeBSD for PowerPC with (much cheaper than the latest gear).My only suggestion is that I would love to see you run the same benchmarks with big-endian Linux, since the entire stack is so much more mature for PPC than LE Linux, which as you mention wasn't even supported for many years.
Anyone running Java workloads in particular has no business using LE Linux when Java itself uses big-endian data formats, and IBM has 15+ years of tuning the JDK for big-endian Linux & AIX.
TL;DR is the biggest advantage of LE Linux is that it's easier to port large custom apps that were written for x86 and have too many byte ordering issues to fix. The original motivation to make the PowerPC architecture bi-endian instead of big-endian was the hope of a Windows NT port. When Apple went their own way with hardware, and IBM focused on servers, little-endian mode disappeared. It's good that POWER8 supports LE mode again, for customers who really need it, but it's far from the normal mode.
PS. I've been working on fixing bugs in Clang/LLVM for PowerPC arch (32/64-bit). FreeBSD recently switched from GCC 4.2.1 (final GPLv2 version) to Clang as the default system compiler on x86, but LLVM has some code gen bugs for PowerPC that I'm hoping to squash. For now, it doesn't work well enough for me to recommend trying to use Clang as an alternative to GCC for POWER8 benchmarking. Certainly not for little-endian mode.
Jake Hamby - Friday, November 6, 2015 - link
BTW, the name of the instruction set architecture is still PowerPC, even though IBM's chips are the POWER series. The predecessor architecture was named POWER, so I always write PowerPC to avoid confusion when referring to the instruction set. The PowerPC 970MP chips in my Quad G5 (2 x dual-core) are a derivative of POWER4.ZeDestructor - Saturday, November 7, 2015 - link
That would be incorrect actually (since they changed since in 2006).The ISA is (currently) named the Power ISA (previously "PowerPC ISA", the "ISA" bit is quite important to denote hardware architecture vs ISA) (with the current being Power ISA 2.07 B)
Underneath each ISA, there are a variety of designs that all have nice, different names, from POWER1-8, PowerPC (including the various variants used by Apple, like the G5/970), Power-PC-AS, Cell, most LSI controllers (mostly PowerPC 440 (Power ISA 2.03) based, afaik) etc.
Source: https://en.wikipedia.org/wiki/Power_Architecture
tipoo - Friday, November 6, 2015 - link
I wish I had a what-if machine to see what IBM would be making had they stayed in the consumer space (well, discounting some consoles they're in - currently only the Wii U on an ancient PowerPC 750 modified for tri-core). And how chunky that PowerBook G5 would have been :Phttp://forums.macrumors.com/attachments/powerbook_...
DanNeely - Friday, November 6, 2015 - link
Probably they'd've ended up making architectural tradeoffs that made their cores a lot more like Intel. As it is, they can optimize their designs for very high power isn't a problem because the power cost is a small fraction of the TCO on one of their monster servers; and a relatively minor concern for consoles (ie just dropping the core count gets them desktop CPU level thermals which are good enough). If they were still selling to Apple, they'd need to be well optimized for performance at only a few watts/core for laptops. Huge L1 caches and massive SMT would be gone because they'd devour battery power to little benefit on systems that generally functioned at very low average CPU loads vs on a mega server or mainframe where if you're not pushing enough work onto it to keep it at a high load level you're doing it wrong.Jake Hamby - Friday, November 6, 2015 - link
Yep. It feels a lot like Apple's own 64-bit ARM cores have approached the old G5 (PPC 970) from the other end of the power envelope.Kevin G - Saturday, November 7, 2015 - link
While Apple's engineers were given the task of a PowerBook G5, they new it could never happen due to thermals and a very arcane chipset. Case in point, the PowerPC 970 could not boot itself: it needed a service processor to calibrate and initialize the frontside bus for the processor before it could take control. Justifiable for servers but unnecessary for a consumer laptop.The expected Powerbook G5's were supposed to be using PA-Semi chips. Due to IBM not meeting Apple's goals, they switched to Intel and the PA-Semi deal fell through with it. However, their dealings with Apple did lead to Apply buying them out a few years later to help design custom ARM SoCs and eventually the custom ARM cores used in the iPhone/iPad of today.
JohanAnandtech - Saturday, November 7, 2015 - link
Would love to hear some thoughts on what the possible problems could arise if we rerun our tests on BE linux. Because our best benchmarks are all all based upon some data stored on our x86 fileservers - so they are probably stored in LE.