A couple months ago, we took a look at the low voltage (LV) server CPU market. At the time, we focused on four-way solutions using two dual-core processors, since those represent the largest slice of the server pie. Our conclusion was that while the power savings brought about by using low voltage CPUs were real, processor choice was only one part of the equation. AMD came out ahead overall in performance/watt, not because they were faster or because their CPUs used less power, but rather because their platform as a whole offered competitive performance while using less power.

We discussed previously exactly what's involved in a low voltage part, but of course the picture is far bigger than just talking about power requirements. Take for example Intel's low-voltage Woodcrest parts; they are rated at 40W compared to the regular Woodcrest parts that are rated at 80W. The price premium for upgrading to a low-voltage part varies; in the case of AMD it's typically anywhere from $100 to $300 per CPU, while on the Intel side some low-voltage parts cost more, the same, or even less than the regular parts (i.e., the Xeon 5140 currently sells for about $450 while the low voltage Xeon 5148 only costs $400). Regardless of price, it's difficult to justify low-voltage processors in terms of power bill savings.

An extra 40W of power in a device running 24/7 for an entire year works out to around $35 per year, so at the low-end of the equation you would need a minimum of three years to recoup the investment (at which point it's probably time to upgrade the server). Other factors are usually the driving consideration.

Saving 40W per CPU socket may not save you money directly in terms of power bills, but generally speaking these chips are going into servers that sit in a datacenter. Air conditioning for the datacenter typically has costs directly related to the amount of power being consumed, so every 40W of power you can save could end up saving another 20W-40W of power in air conditioning requirements. That's still not even the primary concern for a lot of companies, though.

Datacenters often run dozens or even hundreds of servers within a single large room, and the real problem is making sure that there's enough power available to run all of the equipment. The cost of building a datacenter is anything but cheap, and if you can pack more processing power into the same amount of space, that is where low-voltage parts can really become useful. Blade servers were specifically created to address this requirement, and if you can reduce the total power use of the servers by 20% that means some companies could choose to run 20% more servers.

Of course, that doesn't mean that every company out there is interested in running a datacenter with hundreds of computers, so individually businesses need to look at what sort of server setup will best fit their needs. After determining that, then they need to look at low-voltage CPUs and decide whether or not they would actually be helpful. Assuming low-voltage parts are desired, the good news is that it's extremely easy to get them in most modern servers. Dell, HP, and other large server vendors usually include low-voltage parts as an easy upgrade for a small price premium. And that brings us to our low-voltage CPU update.

Intel Quad G-Stepping

Intel doesn't seem to sit still these days, pushing the power and performance envelope further and further. Recently, Intel announced two new G-stepping quad-core parts. The new parts run at the extreme ends of the power consumption spectrum. The first is a 2.0GHz 1333FSB part that runs at 50W while the second is a 3.0GHz 1333FSB part that runs at 120W. There are two main changes to the G-stepping parts, the first of which is power consumption: G-stepping introduces optimizations for idle state power. The second change involves enhancements to the Virtualization Extensions (VT), which mainly improve interrupt handling in the virtualization of Microsoft Windows 32-bit operating systems.

Of course, we would be remiss if we didn't mention AMD's recently launched Barcelona processor here. AMD expects their new quad-core processor to run within the same power envelope as the previous dual-core Opterons, which means twice as many CPU cores potentially without increasing power requirements, resulting in a potential doubling of performance/watt on the socket level. Low-voltage (HE) Barcelona parts will still be available, but even the regular chips include many new enhancements to help with power requirements. We are doing our best to get some additional Barcelona servers in-house in order to test this aspect of the performance/power equation and we hope to follow up in the near future.

One final item worth mentioning is that Intel's 45nm Harpertown refresh of Clovertown is due out in the very near future, which is one more item we can to look forward to testing. Unlike the desktop world, however, acquiring and testing server products often requires a lot more time and effort. Even with the appropriate hardware, the sort of benchmarks we run on servers can often take many hours just to complete a single test, and there are many parameters that can be tuned to improve performance. Since there aren't a lot of early adopters in the server market, though, we should be able to provide you with results before any of the IT departments out there are ready to upgrade. Now let's get on to the testing.

Benchmarking Low Voltage


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  • coolme - Monday, September 17, 2007 - link

    sorry, I meant MCM. Reply
  • Frags - Saturday, September 15, 2007 - link

    AMD has had ample time to scale their processor to a winning choice. MCM was the smartest choice as Intel was bringing in money over the year as AMD showed no competition. Even though Barcelona is still coming (Don't act like it's here already.) AMD is still losing money.

    Even AMD said themselves they wish they had come out with an MCM design with Intel. Unfortunately since they are behind on processor technology it wouldn't have been feasible.

    Even you have said "small, but significant advantage" in other words an advantage that is way too late because they took the long route to revenue. With such a large die size, I can see that yields will still remain low til Intel comes out with definitive competitive beast in very high yields and wide avaiablity. So from a business point of view, AMD is failing. If AMD cannot cut Intels technology lead by half a year, we will continue to see this trend til there is no more AMD.

  • Justin Case - Sunday, September 16, 2007 - link

    Intel's manufacturing lead has been pretty much constant for a decade (if anything, the gap is slightly smaller now).

    AMD has a much bigger market share today than they did in the K7 (and K6, etc.) days. Add the fact that AMD now has some of the best GPUs in the market, a lot of very important patents, an excellent team of engineers and deals with most top OEMs (all things they didn't have back then), and it's pretty obvious that news of AMD's death are greatly exaggerated.

    The problem with AMD is they're trying to grow too fast. To sustain their current growth rate, they're going to have to start turning in a profit very soon (as in under 5 months), which is not very likely.

    If AMD manages to ramp Barcelona to, say, 2.6 GHz in volume until the end of the year (which is not impossible; the issue is related to a respin, not progressive improvement), then the risks they've been taking probably will pay off. Otherwise they'll be forced to slow down and compete based on price, at least until Bulldozer is ready. Their latest GPUs are looking pretty good, too, so they might be able to get by on profits from the ATI division even if Barcelona takes longer to ramp (as I suspect it will).

    In any case, this idea that some people seem to have that AMD is "ruined" and "about to disappear" is complete nonsense. They're in a much better position today than they were in 2002, and they didn't disappear in 2002, either.

    P.S. - A dual-die (2+2) CPU would have been perfectly feasible (just slap a second core on the same package, connected by HT, and treat is as a RAM-less CPU one hop away), and AMD would have easily been able to release it before Intel. It was an executive decision not to do so, and one that I'm sure they regret. The market for quad-core CPUs is small but pretty lucrative. They were probably hoping to have Barcelona out ahead of schedule, and instead it got delayed (hardly something new, chez AMD). On the other hand, I'm sure they're glad they did not go with FB-DIMM (despite having licensed the patents and planned to support it with Barcelona).
  • Brunnis - Friday, September 14, 2007 - link


    Yet, with AMD's native quad core CPU already out, I fail to see why you say that Intel decision was the right one. Had you posted this article a month ago, yes I would have agreed that Intel's quad cores were running rings around AMD, and despite their higher power efficiency in some cases, Intel was winning over all, especially in higher loads. But now, the situation is different - AMD has their own native quad core, which in all likelihood is more energy efficient than the Intel. Thus, your conclusion isnt valid - Intel's choice was right at the time, because AMD could not compete, but now they can, and now its quad core vs quad core, and the fact that AMD's quad core is a single die gives it a small but significant advantage.

    That's not the point. The point is that Intel went with an MCM design and was therefore able to sell quads for almost a year before AMD could provide any competition. Intel made a good decision and just because AMD finally have something to compete with, doesn't make that decision go from good to bad in the blink of an eye. It almost seems as if you believe the tested Intel quad core is a new product. It's not, it's still the old Clovertown core, although it's based on the newer G stepping.
  • Proteusza - Friday, September 14, 2007 - link

    I think thats exactly the point. yes Intel had the overrall performance lead for over a year with their Core 2 architecture.

    And even now, they hold the top spot until Barcelona scales to higher clocks.

    but, in a performance per watt race, they no longer hold the top spot because they no longer have the only quad core cpu.

    Saying that Intel made the right decision in rushing a quad core to market is true. But it only holds true while AMD doesnt have its own quad core. When AMD does, it doesnt really matter who came first - it matters who offers better performance per watt.

    Therefore, now that AMD has quad core chips out, it doesnt matter what Intel did to get theirs out first, it matters which is the best chip.. The Radeon X1950 has been out for longer than the 8800 GTS, does taht mean it is a better graphics card?
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