AMD Phenom II X4 940 & 920: A True Return to Competition
by Anand Lal Shimpi on January 8, 2009 12:00 AM EST- Posted in
- CPUs
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.
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TravisChen - Thursday, January 8, 2009 - link
http://www.anandtech.com/cpuchipsets/showdoc.aspx?...">http://www.anandtech.com/cpuchipsets/showdoc.aspx?...What's the system configuration of the Power Consumption test and which software did you run for loading the system?
Clauzii - Thursday, January 8, 2009 - link
2009 is going to be very interesting for AMD. The foundry layoff should give them some air to breathe and concentrate on the CPU designs.Skobbolop - Thursday, January 8, 2009 - link
AM2 support sounds good, but as far i can see very few mobos with AM2 chipset acually supports phenom CPU's... too bad..i was hoping that i could upgrade with my MSI K9N Platinum.. :(.. this sucks..
Thorsson - Thursday, January 8, 2009 - link
Performance isn't really any better, except in a couple of tests, than C2D chips that are 18 months old, so there's no reason to upgrade for a large chunk of us, and most of the rest will want i7.They need a top end chip that compares to the top end i7 like the 4870 was to the GT280. And this is some way from that. It's like the 4870 was competitive to the 9800GT, and was the same price as well.
With no upgrade path this looks like one strictly for the fanboys at the moment.
calyth - Friday, January 9, 2009 - link
Ha. I'm not quite sure whether I hsould try to respond to this, but sure...It's a non-trivial task to completely redesign the cores themselves, and I'm not even sure whether they could, say cut out the core, and drop in a new one. It's easy for us sideliners to say they need to improve, and quick, but they need to design a new one that has a much better IPC, with speed, not haste.
How is this with no upgrade path? This provides an upgrade path for boards up to AM2, which is good enough. With the AM3 versions coming out, people could drop the AM3 version into an AM2/AM2+ board, wait if necessary until DDR3 prices falls some more, and swap to a newer board with DDR3. And now they've a spare computer.
Look at the i7 prices. Friend of mine just spent 2k for an i7. Sure, he's having fun compiling and playing games with impunity, but I don't think it's the best use of money. Also, C2D is dead. You can't put an i7 into and C2D board, and there's still a good amount of people with older boards that could have a drop in boost.
Atechie - Thursday, January 8, 2009 - link
If the CPU had been relased just after Core2, then it might have been a good CPU.But today, after 2 years, AMD's "native" quadcore still can beat the Core2 clock for clock...that is more than sad.
All Intel needs to do now is slash prices of Yorkfield until their i5 socket 1156 dualchannel DDR3 comes out, and they still got AMD by the balls.
To little, to hyped, to late...
Sunrise089 - Thursday, January 8, 2009 - link
This is silly. If the CPU had come out in Summer '06, it would have been god-like. Quad core vs dual-core, higher clock speed, equal or better overclocking, very competitive clock-for-clock, and on a smaller and cooler process.What you could say was that if it came out right as Peryn launched it would be a close race...but Peryn improved lots of stuff over Conroe, so it isn't fair to say AMD is 2 years behind.
Denithor - Thursday, January 8, 2009 - link
I think that's what Atechie's getting at. Intel took the right path by just cobbling together two dual-core processors to make a quad, while AMD spend excessive time and God only knows how much cash to develop a "monolithic" quad. Which then rolled over and played dead.Hopefully AMD has learned from its mistakes. Otherwise Intel may not have much competition in the near future. What's AMD trading at again, these days?
Proteusza - Thursday, January 8, 2009 - link
I dont know, this doesnt do it for me. I'm a massive AMD fan - I run a 5600+ right now, my previous CPU was an XP 2400+.What is it now, 2 years since the Core 2 Duo was released? And AMD still cant match in clock for clock performance? After the monumental flop that was Phenom, massive delays, poor performance, high power consumption, the TLB bug, patchy backwards compatibility (my MSI K9N mobo with the Nforce 570 SLI chipset cant run AM2+ chips, but the equivalent Asus can), they launch the Phenom II, and the best I can say about it is that is that its acceptable. Acceptable. Not Phenomenal. Just acceptable. Price vs Performance wise, it gets the job done, mostly, sort of. Throw newer game engines at it and even the Q9600, that old workhouse, can beat it.
Its not that Phenom II is a terrible processor. Its not. Its just not what I expected AMD to launch, many months after the flop that was Phenom. I expected something that could at least beat a 65nm Core 2 Duo, if not a Nehalem.
As Anand hinted at, Intel is going to drop prices, which they can afford to, forcing AMD to do likewise, which they cant. AMD's die size is similar yet their margins are far smaller. Intel's next CPU will be the die shrink of Nehalem, what will AMD release? Will it even match Penryn? I can only hope.
KikassAssassin - Thursday, January 8, 2009 - link
Since the Phenom II was always known to just be a die shrink with some optimizations, you were setting your hopes way too high if you thought it was going to compete directly with the i7. AMD needed this launch to keep them in the game, and it looks like it's probably just good enough to be able to do that. We probably won't be seeing any big breakthroughs from AMD until Bulldozer, so we just have to hope that this architecture will have enough headroom in it to last that long.