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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Dmcq - Saturday, May 9, 2015 - link
Well they'll sell where performance is an absolute must but they won't pose a problem to Intel as they won't take a large part of the market and they'd keep prices high. I see the main danger to Intel being in 64 bit ARMs eating the server market from below. I suppose one could have cheap and low power POWER machines to attack the main market but somehow it just seems unlikely with their background.Guest8 - Saturday, May 9, 2015 - link
Uh did you see Anandtech's reviews on the latest ARM server? The thing barely keeps up with an Avoton. Intel is well aware of ARM based servers and has preemptively disARMed the threat. If ARM could ever deliver Xeon class performance it would look like Power8.melgross - Saturday, May 9, 2015 - link
Chip TDP is mostly a concern for the chip itself. Other areas contribute far more waste heat than the CPU does.PowerTrumps - Saturday, May 9, 2015 - link
Power doesn't need to have a TDP of 1000W but 200W is nothing given the performance and efficiency advantage of the processors and Power hypervisor. When you can consolidate 2, 4 and 10 2 socket Intel servers into 1 x 2 socket Power8 server that is 10 x 2 x 135W = 2700 overall Watts vs 400W with the Power server. Power reduces the overall energy, cooling and rack space consumption.KAlmquist - Saturday, May 9, 2015 - link
$4115 E5-2699 (18C, 2.3 Ghz (3.6 Ghz turbo), max memory 768 GB)$5896 E7-8880 (18C, 2.3 Ghz (3.1 Ghz turbo), max memory 1536 GB)
That's a big premium for the E7--enough that it probably doesn't make sense to buy an 8 socket system just to run a bunch of applications in parallel. The E7 makes sense only if you need more than 36 cores to have access to the same memory.
PowerTrumps - Saturday, May 9, 2015 - link
I really enjoyed the article as well as the many data and comparison charts. It is unfortunate that most of your statements, assessments and comparisons about Power and with Intel to Power were either wrong, misleading, not fully explained or out of context. I invite the author to contact me and I will be happy to walk you through all of this so you can update this article as well as consider a future article that shows the true advantage Power8 and OpenPower truly has in the data center and the greater value available to customers.KAlmquist - Saturday, May 9, 2015 - link
I would be surprised if anybody working for Anandtech is going to contact an anonymous commentator. You can point out portions of the article that you think are wrong or misleading in this comment section.To do a really good article on Power8, Anandtech needs a vendor to give Anandtech access to a system to review.
PowerTrumps - Sunday, May 10, 2015 - link
Admittedly I assumed when I registered for the PowerTrumps account some time ago I used a email address which they could look up. But, your point is taken. Brett Murphy with Software Information Systems (aka SIS) www.thinksis.com. Email at bmurphy@thinksis.com. If I pointed out all of the mistakes my comment would look like a blog which many don't appreciate. I have my own blog for that. I like well written articles and happy to accept criticism or shortcomings with IBM Power - just use accurate data and not misrepresent anything. Before Anandtech reviews a Power8 server, my assessment is they need to understand what makes Power tick and how it is different than Intel or SPARC for that matter. Hope they contact me.thunng8 - Sunday, May 10, 2015 - link
I too would like a more detailed review of the Power8.Some of the text in the article made me laugh on how wrong they are.
For example, the great surprise that Intel is not on top.. Well anandtech has never test any Power systems before..
And it is laughable to make any conclusions based on running of 7zip. Just about any serious enterprise server benchmark shows a greater than 2x performance advantage per core in favor of Power compared to the best Xeons. So that 50% advantage is way less than expected.
Btw Power7 for most of its life bested Xeon in performance by very large margins. It is just now that IBM have opened up Power to other vendor that makes it exciting.
JohanAnandtech - Monday, May 11, 2015 - link
I welcome constructive critism. And yes, we only had access to an IBM Power8 dev machine, so we only got a small part of the machine (1 core/2GB)."Some of the text in the article made me laugh on how wrong they are."
That is pretty low. Without any pointer or argument, nobody can check your claims. Please state your concerns or mail me.