The Intel Xeon E7-8800 v3 Review: The POWER8 Killer?
by Johan De Gelas on May 8, 2015 8:00 AM EST- Posted in
- CPUs
- IT Computing
- Intel
- Xeon
- Haswell
- Enterprise
- server
- Enterprise CPUs
- POWER
- POWER8
The Competitor: IBM's POWER8
As we briefly mentioned in the introduction, among all of the potential competitors for the Xeon E7 line, IBM's OpenPower might be the most potent competitor at this time. So how do IBM's offerings compare to Intel's? IBM POWER 8 is a Brainiac (high IPC) design that also wants to be speed demon (high clock speeds).
The POWER8 core can decode, issue and execute and retire 8 instructions per cycle. That degree of of instruction level parallelism (ILP) can not be extracted out of (most) software. To battle the lack of ILP in software, no less than 8 threads (SMT) are active per core. According to IBM,
- 2-threads delivers about 45% performance more than one
- 4-threads deliver yet another 30% boost
- the last 4-threads deliver about 7%
So in total, the 8-way SMT doubles the performance of this massive core. Let us compare the two chips.
| Xeon E7v3/POWER8 Comparison | ||
| Feature | Intel Haswell-EX Xeon E7 |
IBM POWER8 |
| Process tech. | 22nm FinFET | 22nm SOI |
| Max clock | 2.5-3.6 GHz | 3.5-4.35 GHz |
| Max. core count Max. thread count |
18@2.5 GHz 36 SMT |
12@4.2 GHz 96 SMT |
| Max. sustained IPC | 6 (4) | 8 |
| L1-I / L1-D Cache | 32 KB/32 KB | 32 KB/64 KB |
| L2 Cache | 256 KB SRAM per core | 512 KB SRAM per core |
| L3 Cache | 2.5 MB SRAM per core | 8 MB eDRAM per core |
| L4 Cache | None | 16 MB eDRAM per MBC (64/128 MB total) |
| Memory | 1.5 TB per socket (64 GB per DIMM) |
1-2 TB per socket (64 GB per DIMM) |
| Theoretical Memory Bandwidth | 102 GB/s (independent mode) |
204 GB/s |
| PCIe 3.0 Lanes | 40 Lanes | 32 Lanes |
The POWER8 looks better than Haswell-EX in almost every spec, but the devil is of course in the details. First of all, Intel's L2-cache works at the same clock as the core, IBM's L2-cache runs at a lower clock (2.2 GHz or less, depending on the model). Secondly, the POWER8's L3 eDRAM cache might be much larger, but it is so also a bit slower.
But the main disadvantage of the POWER8 is that all this superscalar wideness and high clockspeed goodness comes with a power price. This slide from Tyan at the latest OpenPOWER conference tell us more.
A 12 core POWER8 is "limited" to 3.1 GHz if you want to stay below the 190W TDP mark. Clockspeeds higher than 4 GHz are only possible with 8-cores and a 250W TDP. This makes us really curious what kind of power dissipation we may expect from the 4.2 GHz 10-core POWER8 inside the expensive E870 Enterprise systems (300W?).
That is not all. Each "Jordan Creek2" memory buffer on the Intel system is limited to about 9W. IBM uses a similar but more complex "Centaur" memory buffer (including a 16 MB cache) which needs more than twice as much energy (16-20W). There are at least four of them per chip, and a high-end chip can have eight. So in total the Intel CPU plus memory buffers have a 201W TDP (165W CPU + 4x9W Jordan Creek 2), while the IBM platform has at best a 270W TDP (190W CPU+ 4x20W MBC).
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PowerTrumps - Saturday, May 9, 2015 - link
Ok, yes a data center like Verizon or ATT might not "qualify" but the point is accurate. I work with IBM's Power servers and have absolutely consolidated 5 racks of x86 into a single Power server - it was 54 Intel 2S & 4S servers into a single 64c Power7. Part of this is due to the "performance" of Power but most of the credit goes to the efficiency of the Power Hypervisor. PHYP can provide a QoS to each workload while weaving a greater amount of workloads onto fewer Power servers/cores than what the benchmarks imply.newtrekemotion - Friday, May 8, 2015 - link
I wouldn't discount Oracle so quickly. The T5 was a pretty big step forward from the T4 and the new M7 chip sounds like it could be quite the competitor with 2 TB of memory per socket and 32 cores, especially for highly threaded loads since an octo-socket system would have 2048 threads and support 16 TB of memory.. Hopefully this can bring some more competition to the market, though with only Oracle and Fujistu (maybe?) selling systems it won't have quite the impact that multiple POWER8 vendors could bring. Love them, hate them, or anywhere in between it seems Oracle is not ready to give up in this arena and it looks like they are putting more effort in than Sun was (or are at least executing on effort more than Sun did).Something else to note here is the process advantage that Intel has over everyone else. I might have missed it in the article, but especially for performance/watt this is important.
In all I think the statement at the beginning of the article that this area is getting more exciting is very true. Just seems like it might be a 3 way race instead of a 2. The recent AMD announcement that they wanted to focus on HPC is interesting too though of the 4 (Intel, IBM, Oracle and AMD) they have the furthest to go and the fewest resources to do it with. The next few years are going to be very interesting and hopefully someone, or a combination can push Intel and drive the whole market forward.
JohanAnandtech - Friday, May 8, 2015 - link
I was writing from a "who will be able to convert Intel Xeon people" point of view. As I wrote in the Xeon E7v2 article, Oracle's T processors have indeed vastly improved. That is all nice and well but there is no reason why someone considering a Xeon E7 would switch. Oracle's sales seems to mostly about people who are long time Oracle users. As far as I can see, OpenPOWER servers are the only real thread to Intel's server hegemony.Kevin G - Saturday, May 9, 2015 - link
Oracle does offer one reason to switch to SPARC: massive licensing discounts on Oracle software.If you're not using Oracle's software, then yeah, the SPARC platform is a very tough sell over x86 or POWER.
JohanAnandtech - Saturday, May 9, 2015 - link
exactly. Good point.PowerTrumps - Saturday, May 9, 2015 - link
If you are running Oracle software you should know that IBM and Power are the largest platform which Oracle software runs on. Secondly, if running Oracle products licensed by the core, the only platform to control Oracle licensing is Power (not including Mainframe in this assertion). I have reduce Oracle licensing for customers anywhere from 4X to 10X. Do the math on that to appreciate those savings. Lastly, when I upgrade customers from one generation to another we talk about how much Oracle they can reduce. You don't hear that when upgrading from Sandy Bridge to Ivy Bridge to Haswell.kgardas - Friday, May 8, 2015 - link
I'm not sure about T5, but certainly latest Fujitsu's SPARC64-X+ is able to over-run POWER8 and by wide margin also older Xeon's. Just look for the spec. rate. It also won some SAP S&D 2-tier benchmark on absolute performance so I'm glad that SPARC is still competitive too...Kevin G - Saturday, May 9, 2015 - link
The top SPARC benchmarks I've seen are using far more sockets, cores, threads and memory to get to that top spot. It is nice that the system can scale to such high socket counts (40) but only if you can actually fund a project that needs that absolute performance. Drop down to 16 socket where you can get twice the performance from POWER than SPARC with the same licensing cost, what advantage does SPARC have to make people switch?Even then, a system like SGI's UV2000 would fall into the same niche due to its ability to scale to insane socket counts, software licensing fees be damned.
kgardas - Tuesday, May 12, 2015 - link
Kevin G, actually you are right and I made an mistake. It was not intentional, I was misled by spec site claiming "24 cores, 4 chips, 6 cores/chip, 8 threads/core" for "IBM Power S824 (3.5 GHz, 24 core, RHEL)" so I've thought this is 4 socket setup and I compared it with Fujitsu M10-4 which won. Now, I've just found IBM is two socket which means it wins on socket/spec rate basis of course. Price-wise IBM is also way much cheaper than SPARC (if you don't run Oracle DB of course) so I keep my fingers crossed for OpenPOWER.Honestly, although this is really nice to see I still have kind of feeling that this is IBM hardware division swan's song. I would really like to be wrong here. Anyway, I still think that ARMv8 does have higher chances in getting into the Intel's business and be really a pain for Intel. On the other hand if OpenPOWER is successful in Chinese business, that would be good and some chance for us too to see lower-cost POWER machines...
PowerTrumps - Saturday, May 9, 2015 - link
yes, take a look at those benchmark results and you see the Fuji M10-4S requires 640 & 512 cores. Even the Oracle M6-32 uses 384 cores. The Fuji 512c example had 33% higher SAPS with 2X the cores. The M6-32 has 50% more cores to get 21% higher SAPS. Further, looking at the SAP benchmark as a indicator of core, chip & server performance shows that SPARC & Intel are roughly 1600 - 2200 SAPS per core compared to Power8 which is 5451 SAPS for the 80 core E870. So you put this into context the 80 core Power8 has slightly less than 1/2 the SAPS of the 640 core Fujitsu M10-4S. Think of ALL the costs associated with 640 cores vs 80...ok, 160 if we want to get the SAPS roughly equal. 4X more cores to get less than 2X the results.