Intel Xeon 7460: Six Cores to Bulldoze Opteron
by Johan De Gelas on September 23, 2008 12:00 AM EST- Posted in
- IT Computing
Power
The Opteron may have a slight disadvantage here as it has a 1200W PSU instead of a 1000W unit. We had no choice as our 1U server with 1000W PSU that we used in our previous reviews is not supported by ESX. Our Supermicro SC828TQ-R1200LPB 2U works very well with ESX, but it may consume a few extra Watts. (Or perhaps not - without testing both PSUs we really don't know their efficiency curves.) All Xeons use the exact same chassis, motherboard and power supply. We decided to test with both 16GB and 32GB. In our benchmarking scenario we only needed 16GB, as our VMs were very processing intensive and didn't need more memory. In the real world, it is much more likely that most of your VMs need far less processing power and will require more memory (especially when you run more VMs). The extra data point allows you to understand how much power eight extra DIMMs require, allowing you to estimate how much power your setup will consume.
| System Power Comparison | |||
| Typical CPU load | Power with 6 VMs at full load (16GB) |
Power with 6 VMs at full load (32GB) |
|
| Xeon 7330 (2.4GHz) | 91-96% | 456 | 541 |
| Xeon 7350 (2.93GHz) | 90-95% | 605 | 692 |
| Xeon X7460 (2.66GHz) | 85-90% | 502 | 587 |
| Opteron 8356 (2.3GHz) | 95-99% | 485 | 534 |
It's amazing to see that the 6-core X7460 is capable of staying well below its older 65nm brother, the X7350 at 2.93GHz. Both CPUs have the same TDP, but the 6-core X7460 consumes 25W less per CPU than the X7350. Part of this can be explained by slightly lower CPU usage as the 24 cores do not have to work as hard to handle the six VMs. The X7460 is a huge chip, but that does not prevent the newest Xeon from performing 45% better while consuming 25W less per CPU.
| Transactions per Watt | |
| Xeon 7330 (2.4GHz) | 3.93 |
| Xeon 7350 (2.93GHz) | 3.26 |
| Xeon X7460 (2.66GHz) | 5.59 |
| Opteron 8356 (2.3GHz) | 5.26 |
This table also helps explain why it is so important for Intel not to wait for a Xeon Nehalem MP to regain the performance crown. The current Xeon 73xx MP line takes a serious beating from the Opteron when it comes to virtualized performance/Watt. However, this table also makes it clear that the current Opteron has no chance of beating the 45nm Xeon MP. If we use the 8360SE (2.5GHz) instead of the 8356, performance will rise 8% at the most, but power consumption will probably increase by 20-30%, resulting in an even worse performance/Watt result.
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npp - Tuesday, September 23, 2008 - link
I didn't got this one very clear - why should a bigger cache reduce cache syncing traffic? With a bigger cache, you would have the potential risc of one CPU invalidating a larger portion of the data another CPU has already in its own cache, hence there would be more data to move between the sockets at the end. If we exaggerate this, every CPU having a copy of the whole main memory in its own cache would obviously lead to enormous syncing effort, not the oposite.I'm not familiar with the cache coherence protocol used by Intel on that platform, but even in the positive scenario of a CPU having data for read-only access in its own cache, a request from another CPU for the same data (the chance for this being bigger given the large cache size) may again lead to increased inter-socket communication, since these data won't be fetched from main memory again.
In all cases, inter-socket communication should be much cheaper than the cost of a main memory access, and it shifts the balance in the right direction - avoiding main memory as long as possible. And now it's clear why Dunnington is a six- rather than eight-core - more cores and less cache would yield a shift in the entirely opposite direction, which isn't what Intel is needing until QPI arrives.
narlzac85 - Wednesday, September 24, 2008 - link
In the best case scenario (I hope the system is smart enough to do it this way), with each VM having 4 CPU cores, they can keep all their threads on one physical die. This means that all 4 cores are working on the same VM/data and should need minimal access to data that another die has changed (if the hypervisor/hostOS processes jump around from core to core would be about it). The inter-socket cache coherency traffic will go down (in the older quad cores, since the 2 physical dual cores have to communicate over the FSB, it might as well have been the same as an 8 socket system populated by dual cores)Nyceis - Tuesday, September 23, 2008 - link
Can we post here now? :)JohanAnandtech - Wednesday, September 24, 2008 - link
Indeed. As the IT forums gave quite a few times trouble and we assume quite a few people do not comment in the IT forums as they have to register again. I am still searching for a good solution as these "comment boxes" get messy really quickly.Nyceis - Tuesday, September 23, 2008 - link
PS - Awesome article - makes me want hex-cores rather than quads in my Xen Servers :)Nyceis - Tuesday, September 23, 2008 - link
Looks like it :)erikejw - Tuesday, September 23, 2008 - link
Great article as always.However the performance / watt comparison is quite useless for virtualization systems though since they scale well at a multisystem level and for other reasons too
I won't hurt to make them but what users really care of is performance / dollar (for a lifetime)
Say the system will be in use for 3 years.
That makes the total powerbill for a 600W system about 2000$, less then the cost of one Dunnington and since the price difference between the Opteron and Dunnington cpus is like 4800$ you gotta be pretty ignorant to choose system with the performance / watt cost.
Lets say the AMD system costs 10000$ and the Intel 14800$(will be more due to Dimm differences) and have a 3 year life then the total cost for the systems and power will be 12000 and 16800.
That leaves us with a real basecost/transaction ratio of
Intel 5.09 : 4.25 AMD
AMD is hence 20% more cost effective than Intel in this case.
Any knowledgable buyer has to look at the whole picture and not at just one cost factor.
I hope that you include this in your other virtualization articles.
JohanAnandtech - Wednesday, September 24, 2008 - link
You are right, the best way to do this is work with TCO. We have done that in our Sun fir x4450 article. And the feedback I got was to calculate on 5 years, because that was more realistic.But for the rest I fully agree with you. Will do asap. How did you calculate the power bill?
erikejw - Wednesday, September 24, 2008 - link
Sounds good, will be interesting.The calculations was just a quick and dirty 600W 24/7 for 3 years and using current power prices.
VM servers are supposed to run like that.
It would also be interesting to see how the Dunnington responds when using more virtual cores than physical. Will the decline be less than the older Xeons?
What is a typical (core)load when it comes to this?
The Nehalems will respond more like the Athlons in this regard and not loose as much when the load increases, at a higher level than AMD though.
I realised the other day that it seems as AMD have built a servercpu that they take the best of and brings to the desktop market and Intel have done it the other way around.
The Nehalems architechture seems more "serverlike" but will make a bang on the desktop side too.
kingmouf - Thursday, September 25, 2008 - link
I think this is because they have (or should I say had) a different CPU that they wanted to cover that space, the Itanium. But now they are fully concentrated to x86, so...