Power Consumption

The Magny-Cours Opteron arrived one week ago, which is barely enough time to do virtualization benchmarking. So we have to postpone extensive power testing to a later date. The Opteron 6174 came in a desktop reference system which is in no way comparable to our Xeon X5670 1U server. We do have an six-core Opteron based system which is very similar to the Opteron 6174 reference system: the motherboard is also equipped with the new AMD SR5670 chipset and housed in the same desktop system. We can tell you that the idle power of the Opteron 6174 is a few watts lower than the six-core Opteron 2435. Both throttle back to 800 MHz, but the Opteron 6100 series gets a real C1E mode.

C1E mode can only be entered if all CPUs are idle. In a dual socket system, both CPUs enter C1E or they don’t. C1E mode is entered only after longer periods of inactivity. All cores flush their L1 and L2 caches to the L3-cache. Then all cores are clockgated (C1). Once that happens, the Hyper Transport links are put in a lower power state. This allows the chipset to enter a lower power state as well. Only when all these previous steps are done, both sockets are in C1E. DMA events will make the sockets go out of the C1E state. So C1E probably won't happen much on server systems. The C1E state is only entered if absolutely no processing is happening at all.

The C1E mode can reduce power quite a bit:

  • Core clocks are turned off (Clockgate C1 state)
  • L3, North Bridge, and memory controller all divide their clock frequencies (but are not clockgated!)
  • All HyperTranspor links transition to LS2 low power state (LDT_STOP_L)
  • DRAM DLL’s disabled
  • Memory Transitions from precharge power down mode to self refresh mode (low power)

According to AMD, at full load a 1.7GHz 65W ACP Opteron 6164 HEwould consume about 4% more power than a 2.1 GHz 55W ACP 6-core Opteron 2425 HE. AMD measured 225W for  the former, 215W for the latter. We measured 263W on the same system at full load with an Opteron 6174. That's 48W more, or about 24W per CPU. Assuming that the low power CPUs were running at their ACP (65W), we can conclude that the 2.2 GHz Magny-Cours needs about 89W. While the new twelve-core Opteron clearly needs a bit more power than the six-core Opteron, it's not a dramatic increase.

HPC and Encryption Benchmarks Final Words


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  • 564265425722557 - Monday, March 29, 2010 - link

    1. Why is the TDP of the 65W ACP Magny Cours the question mark? And are you sure the TDP of the 80W ACP ones 115W?

    2. The Intel systems have only 24GB ram against the 32GB ram on the 2S magny cours. That's why the 100GB database test favors the Magny cours by a large margin.
  • JohanAnandtech - Monday, March 29, 2010 - link

    AMD told us the TDP values of the Magny-Cours at 80 and 105W ACP. The TDP values of the Lower power versions were not disclosed yet.

    And as we disclosed on the benchmark config page, none of the benches uses more than 20 GB. The vAPus mark I uses about 19 GB. The SQL Server uses much less. While the SQL server test has to scan through the complete index, it does access the complete 100 GB data. There absolutely no advantage for the Opterons there. We checked.

    The fact that we spec the servers like that is a direct consequence of their memory channels (3 and 4). There is not much we can do about that.
  • Penti - Tuesday, March 30, 2010 - link

    How about about 4P performance? It's cheap now and it's AMD whole selling point. I guess you can get a 4P 48-core 128GB system for not that much. How would that compare to a say 2P Nehalem 12-core 92GB? Wouldn't they cost about the same? Will it still be competitive against 8-core 2P Nehalem-EX? And how about the 4P (like 6-core versions) Nehalem-EX? How about the 8-core versions of 6100 series Opterons? Reply
  • elnexus - Wednesday, March 31, 2010 - link

    In answer to cost:

    Compare our 2P Xeon 5600-series Workstation :http://elnexus.com/products.aspx?line_id=15514
    with our 4P Opteron 6100-series Workstation: http://elnexus.com/products.aspx?line_id=15635

    (I hope this isn't condemned as advertising, since it is an attempt to answer a question about price vs performance.)

    Note how low priced the 6128 chip is (the default chip included in the base price).

    AMD, I think are running away from Intel if you factor in the price...
  • Penti - Wednesday, March 31, 2010 - link

    Thanks, I don't condemn it as advertising as this is a new platform so it's interesting and hard to get prices for complete systems yet. Basically 4P 8-core 6100-series opterons with 128GB DDR3 ECC REG cost as much as 2P six-core Xeon (Westmere EP) with 96GB DDR3 ECC REG. Mainly because you can use cheaper 4GB sticks and still get 128GB. And partly because there's no longer any markup for above >2P parts. I guess it accounts for something. Yeah, 6128 chip virtually don't cost nothing for being 4P compatible. Guess it helps AMD for a lot of workload scenarios. And since you can get 4P in 1U it's really nothing that speaks against it. Will be interesting to see what the Nehalem-EX can do though. Reply
  • TitanusComp - Wednesday, April 06, 2011 - link

    You can really get a good idea by comparing this two products:

    48 Cores:

    24 Cores (Quad SLi Capable)

    Now, things to consider, do you need CPU or GPU power?
  • duploxxx - Monday, March 29, 2010 - link

    To make the whole benchmark complete I think you should ask some AMD Opteron 6136 from AMD to get a full review. Reply
  • duploxxx - Monday, March 29, 2010 - link

    and add the 56xx 4core counterpart off course Reply
  • JohanAnandtech - Tuesday, March 30, 2010 - link

    We are working on it. Expect an update with new SKUs this month. I would say next week, but I would like to take some time to do some in depth analysis. Reply
  • Hacp - Monday, March 29, 2010 - link

    I want to ask why are you biased against AMD? You should base your tests based on price. AMD is selling their 12 core for the price of an Intel 6 core. Compare apples to apples! Do a 12 core vs 6 core comparison and see who wins. Otherwise, you are doing a disservice.

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