45nm and Low Power Consumption

Built on a 45nm process, Phenom II is finally using the same feature size as Intel’s processors. Intel’s 45nm caches are a bit smaller than AMD’s, but it’s no longer a 65nm vs. 45nm playing field - things are much more even. However, AMD and Intel’s approaches to 45nm differ considerably.

Circuits are placed on silicon wafers through the use of photolithography. Light is shone on a mask, and the light then makes it through the mask and etches the circuits on the silicon wafer. The wavelength of light used determines the minimum feature size of the circuits on the wafer. By itself, 193nm wavelength deep ultra-violet light is only useful for circuit feature sizes down to 50nm. To reach 45nm and beyond you need to do a little more.

AMD uses immersion lithography, which places a liquid between the source of the light and the wafer itself. The liquid increases the resolution at which the light can focus, allowing for smaller than 50nm feature sizes with currently available tools. Immersion lithography isn’t a performance enhancing feature; it’s simply one that makes it possible for AMD to manufacture at 45nm.

Intel claims that immersion lithography isn't necessary at 45nm and doesn't use it. Intel uses a technique known as double patterning but only on the gate layer of the chip. Intel’s approach requires higher mask costs but can result in a high yield 45nm chip without the use of immersion lithography. AMD’s approach should be more cost effective initially since you have to create fewer masks, but Intel’s scale of 45nm production should help offset that. For what it's worth, the double patterning has been in use since Intel's 65nm process.

Remember Intel’s high-k + metal gate transistor announcement? That’s still a feature advantage that Intel holds at 45nm. The new transistors make sure that current doesn’t flow when it’s not supposed to, reducing power consumption.

The two processes, despite both being 45nm, are different enough that they aren't the same despite having similar feature size - but comparing manufacturing processes is beyond the scope of this article.

A Power Efficient Phenom?

When Phenom first hit, not only was it underperforming, but it also drew far too much power. Combine that with a CnQ mode that robbed users of performance and you ended up with a CPU that was hardly power efficient. Just like the cache deficiency, Phenom II fixes this.

With Core i7, Intel developed power gate transistors that can completely shut off an individual core that’s not in use. Intel’s cache hierarchy is inclusive so any data stored within a core’s L1 and L2 caches is already duplicated in the L3 cache; if a core isn’t in use it can be shut down and there’s no need to wake it back up until it’s needed again.

Remember, Phenom II isn’t a complete redesign, so AMD couldn’t work on a similar technology. Despite that, idle power in Phenom II is greatly improved. When a single core is idle, the contents of its L1 and L2 can be flushed out to L3, allowing the processor to halt the clocks to that core - thus reducing power. The core will still consume leakage power, but it’ll be far less than if it were running at the lowest p-state. Intel introduced something similar back in the Conroe days, except data from L1 was pushed out to L2 before the core was powered down since there was no L3. Nehalem still has the ultimate in idle power thanks to Intel’s power gate transistors, but as you can see below Phenom II’s idle numbers are quite impressive.

Processor Idle Power Load Power
AMD Phenom II X4 940 (3.0GHz) 109.6W 189.7W
AMD Phenom 9950 BE (2.6GHz) 124.2W 210W
AMD Phenom X3 8750 (2.4GHz) 127.5W 210W
AMD Athlon X2 6400 (3.2GHz) 101W 195W
Intel Core i7-965 (3.2GHz) 99W 199W
Intel Core i7-920 (2.66GHz) 95W 168W
Intel Core 2 Extreme QX9770 (3.2GHz) 135W 219W
Intel Core 2 Quad Q9400 (2.66GHz) 126W 174W
Intel Core 2 Quad Q8200 (2.33GHz) 134W 168W
Intel Core 2 Duo E8600 (3.33GHz) 124W 157W

Note that while Penryn’s idle power isn’t nearly as low as Phenom II, this has more to do with Penryn’s lowest operating frequency. Phenom II’s minimum p-state is only 800MHz, compared to 2.0GHz on Penryn. Load power is also impressive, not quite Nehalem impressive but definitely competitive with Penryn at least.

In load power, Penryn still has the advantage. The Q9400 draws 174W compared to 190W for the Phenom II X4 940. The Core i7 is still the most power efficient of the two, as the i7-920 draws less power and is faster than the Phenom II X4 940.

Finally, Cool 'n' Quiet You Can Use Socket-AM2, AM2+ and AM3: Backwards Compatibility
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  • Shadowmaster625 - Friday, January 16, 2009 - link

    Why didnt you include an overclocked E5200 in the testing?!?!?!

    omg this is horrid. How do these $230-$270 CPUs compare to an $85 E5200 coupled with a $105 Gigabyte GA-EP45-UD3R? That combo will easily overclock to 3.8 Ghz on stock cooling. CPU, mobo + RAM all for less than the cost of a Phenom II. And better performance too.
    Reply
  • Reynod - Monday, January 12, 2009 - link

    Another excellent article Anand.

    Would you be able to write a short piece on the AM3 socket and the "likely" impact on performance once you have some samples please?

    Reply
  • R4F43LZiN - Saturday, January 10, 2009 - link

    I wanted to see some Phenom II overclocked gaming benchmarks... Reply
  • zagortenay - Saturday, January 10, 2009 - link

    To correct my mistake in above post:
    "And check the link of very respectable "Guru of 3D" yourself, X4 940 beats Core i7 920 in higher resolutions." Not Core i7 940.
    Reply
  • zagortenay - Saturday, January 10, 2009 - link

    Great comments Aranthos! AMD did a great job with Phenom II, no doubt about that.
    Anandtech review is kind of fair and balanced when it comes to giving the final verdict, but the tests are deceiving and unfair as usual.
    First of all, as somebody else has already pointed out, they used an average mobo to test Phenom II, while they used expensive enthusiast level mobos for Core2 Quad and Core i7 (230 and 250 Dollars respectively). They could not find an Asus M3A79-T (which is much cheaper at 185$) There is no excuse for that! Either a deliberate move not to show what Phenom II can deliver at its best, or Anand needs to learn a lot from us. Just check the below link to see the performance difference between 790GX and 790FX. Quite some performance difference in some benchmarks and consider that it is still a close competition with an average AMD motherboard.
    There IS a difference apparently: http://www.legitreviews.com/article/795/5/">http://www.legitreviews.com/article/795/5/ and it would change some conclusions
    And now introducing a classic: Why Core2 Quads run on DDR3 (Yeah, all Core2 Quad users definitely switched to DDR3, lol!) and Phenom IIs run on DDR2? To show the best of Core 2 Quads... So what happens if DDR2 is used also on Core 2 Quads? See yourself below. X4 940 beats Q9550 most of the time and even Q9650 in some applications.
    http://www.bit-tech.net/hardware/2009/01/08/amd-ph...">http://www.bit-tech.net/hardware/2009/0.../amd-phe...
    I wander what trick they will do with RAMs, when Phenom II AM3 (with DDR3) comes this February.
    Anand says X4 940 trails Q9650 and by 28.4% when it comes to Far Cry 2. Is it so? Or? Check the above link again. Even with DDR3 RAMs Q9650 leads by only 4.4%. With DDR2, X4 940 leads this time, with a little margin. Same resolution! Who to beleive?
    And check the link of very respectable "Guru of 3D" yourself, X4 940 beats Core i7 940 in higher resolutions. He he!
    http://www.guru3d.com/article/amd-phenom-ii-x4-920...">http://www.guru3d.com/article/amd-phenom-ii-x4-920...
    So what? Don't get fooled, don't get deceived by the "big brother connections".
    Final words: Yes I am a fan boy and I don't pay a penny for Intel!
    Reply
  • Aranthos - Saturday, January 10, 2009 - link

    I wonder why so many people keep saying "What happened to the AMD from the Athlon64 era? It was whupping Intel!" etc.

    That AMD is still here. The same AMD that so long ago brought us Hypertransport, the integrated memory controller, native dual-core and the like brought us native quad-core and a three level cache heirarchy a full year before Intel did either. As it turned out, Intel did it better - a fact with which I won't even try to argue. However, AMD is still working.

    P1 flopped. It was the most hyped chip in years, and brought all sorts of false promises. All Deneb promised was better overclocking, lower power consumption and more clock-for-clock performance. It did all 3.

    I'm not going to say Intel ripped off AMD by using an IMC and a HT-esque high speed interconnect. Granted, AMD did it first, but Intel would have ended up doing it ANYWAY because it is a good idea.

    Back to the original topic - we still have the old AMD with us. They're still innovating as always. But, we have a new Intel. One that isn't peddling crappy Netburst chips. New Intel is going out guns blazing, and they have the money to make sure that another P4 doesn't happen.

    AMD got lucky back in the P3 -> P4 era. They're gonna have to either pull out a win of epic proportions, or stick to razor thin margins on their chips. Intel has seriously deep pockets, and can easily afford to destroy AMD's prices.

    i7 is epic win. But I'm buying a Deneb anyway. Yeah, people are gonna call me a fanboy, and so what. I'm buying a chip made by a company that is facing a company over 50x their size. While they're not a little family run business, I will support them to their dying breath because they need every sale they can get. I like high performance as much as the next guy, but if buying higher performance (in my case at a higher price [I have an AM2+ motherboard]) puts the business a step closer to being one-sided, then Intel can suck it. They don't need my money.
    Reply
  • Mathos - Saturday, January 10, 2009 - link

    Well, it's not quite a 4800 series equivelent release this time. More like being around the same as the 3800 series was. A good improvement over the hd2000 series cards, in this case a good improvement over the phenom 1.

    On the other hand I am wanting to see what will happen with the AM3 versions. Should improve scores quite a bit on anything that likes memory speed and bandwidth. I'm also wondering what other optimizations will come with AM3. Gonna wait for that, since I should be getting another nice quarterly bonus around the time those come out. Use a pII 945 on my old k9a2 plat till I can get an AM3 board and DDR3 memory.
    Reply
  • Maroon - Saturday, January 10, 2009 - link

    This was a great step forward by AMD. After the Phenom flop they had to transition successfully to 45nm or basically fold. They have done that. AMD doesn't have the resources to compete with Intel on the highend right now, but with this release they can compete in the mainstream market where most processors are sold.

    They're using the same strat that worked for the 4xxx series video cards, performance per dollar.

    Reply
  • Megaknight - Friday, January 09, 2009 - link

    Have the Intel fanboys noticed that they're comparing a DDR 2 Phenom II to a DDR 3 i7? I know AMD will be slower anyway, but it should close the gap a bit, right? Reply
  • aeternitas - Friday, January 09, 2009 - link

    Are you serious? DDR3 might be able to give AMD an advantage overall compared to the C2. But then going DD3 and spending that much money, you might as well go i7 anyway. (unless you're a fanboy)

    Seriously guys, if you're going t go around comparing P2 to the i7, you need to focus on price! Else you'll look really bad.

    P2 is against C2. End of story. You cant sit around theorizing some magical item is going to get a P2 anywhere close to the i7.

    Stop defending AMD. They have 18 months of catchup to do and dont need pats on the back and excuses from people like you. They have a good chip and alot of good things in the chip that they dont need to do in the future as they come up with new architecture.
    Reply

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