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
The Phenom Inspired, Core i7-like, Phenom II
Want to hear something funny? When AMD launched the original Phenom, it was a unique looking architecture, something AMD touted as a significant advantage due to its "native" monolithic quad-core design (four cores, one die). I often argued that it wasn't an advantage, simply because the performance numbers didn't back up AMD's claims. AMD never won a real world desktop benchmark because of the monolithic quad-core design.
Intel followed up with Nehalem (Core i7), a microprocessor that had a very Phenom-like cache hierarchy (four cores, private L2 caches, one large shared L3 cache), but with much better performance.
Phenom II builds upon the same architecture as the original Phenom, hardly changed, but improves on a few key limitations. This isn't a new microarchitecture, this is a 45nm shrink of Phenom. In a sense, AMD gave up on improving the original Phenom. Early on after Phenom's release AMD went head in the sand and did whatever was necessary to make the 45nm transition perfect. Deneb, as it was called internally, had to succeed - because AMD as a company wasn't going to survive on the backs of the GPU division forever. It's somewhat ironic that Intel was able to execute a better Phenom-like microarchitecture before AMD.
| Processor | AMD Phenom II | AMD Phenom | Intel Core i7 | Intel Core 2 Quad Q8xxx/Q9xxx |
| Manufacturing Process | 45nm | 65nm | 45nm | 45nm |
| L1 Cache | 64K + 64K per core | 64K + 64K per core | 32KB + 32KB per core | 32KB + 32KB per core |
| L2 Cache | 512KB per core | 512KB per core | 256KB per core | 2x3MB, 2x4MB or 2x6MB |
| L3 Cache | 6MB | 2MB | 8MB | - |
| Transistor Count | 758M | 450M | 731M | 456M (6MB/8MB L2) or 820M (12MB L2) |
| Die Size | 258 mm2 | 285 mm2 | 263 mm2 | 164 mm2 (6MB/8MB L2) or 214 mm2 (12MB L2) |
The above chart details the specifications for the current AMD and Intel quad-core offerings, and here we see a problem. Phenom II and Core i7 are around the same die size and have similar transistor counts, yet Core i7 sells for $284 - $999 while Phenom II sells for $235 - $275. The part that Phenom II actually competes with is the Core 2 Quad Q9400 (and perhaps the Q9550; more on that later), and that's a ~36% smaller die. This is the downside to AMD's pricing strategy; while it's great for consumers it's not particularly great for AMD's profit margins. The other thing to keep in mind is that at 214 mm2 Intel has an entire line of quad-core processors that, in theory, could be moved down the price list if the price wars of 2008 were to continue into 2009.
The move to 45nm was severely needed as you can see by the table above. AMD and Intel seem to agree on the right way to build a quad-core processor today: four cores with individual L2 caches (or one shared L2 per two cores on Intel) behind a large global L3 cache. Intel, however, waited until the 45nm transition was complete to move to that sort of an architecture in order to outfit the chip with a large enough L3 cache. AMD jumped the gun early with Phenom and was forced to limit its L3 cache size to 2MB on 65nm. Finally, with the move to 45nm, Phenom II boasts a 6MB L3.
The transistor counts of Phenom II and Core i7 are surprisingly close, as are the die sizes. The two chips are designed completely differently, but the end result is similarly sized processors. Note that both Phenom II and Core i7 are too big for high volume mainstream markets; the die size would need to be around half of what it is now to address those markets. AMD and Intel will do so by introducing dual (or triple in the case of AMD) core versions at 45nm and then transitioning almost exclusively to quad-core at 32nm.
Phenom II also marks AMD's return to the >$200 CPU market. The two parts launching today are the Phenom II X4 940 and the Phenom II X4 920, priced at $275 and $235 respectively.
| Processor | Clock Speed | Uncore Clock | L2 Cache | L3 Cache | TDP | Price |
| AMD Phenom II X4 940 | 3.0GHz | 1.8GHz | 2MB | 6MB | 125W | $275 |
| AMD Phenom II X4 920 | 2.8GHz | 1.8GHz | 2MB | 6MB | 125W | $235 |
| AMD Phenom 9950 | 2.6GHz | 2.0GHz | 2MB | 2MB | 140W | $174 |
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Spoelie - Thursday, January 8, 2009 - link
Only one little gripe: why was a mid-range motherboard used for the phenom while the intel processors got enthusiast versions?there IS a difference apparently: http://www.legitreviews.com/article/795/5/">http://www.legitreviews.com/article/795/5/
Not that it would change the conclusions.
melgross - Thursday, January 8, 2009 - link
"Not that it would change the conclusions. "You answered your question yourself.
duploxxx - Thursday, January 8, 2009 - link
Nice review, always my firts site to read for a review. A bit basic on oc potential but you hint there is more to come, lets hope we don't have to wait another month like we had to wait for the 790GX board reviews.I don't see why AMD launched the unicore @1.8ghz.
You are stating that it is because of yields, might be but shanghai launched @2.0-2.2. Phenom2 would scale a lot better performance wise against penryn with a 2,2GHZ NB speed. for sure on the BE part that is a real advantage against the q9400-Q9550
Is this to give the am3+ an additional performance gain when launched? Retail chips hit NB speeds of 2,4-2,6 easy, they also showed up to 3.5-3.6ghz oc on stock vcore, your oc gain was real low, perhaps you show in future oc review what phenom can actually do.
no overview of total system power consumption idle and load?
ssj4Gogeta - Thursday, January 8, 2009 - link
Since most of the people have Intel now, it'll take them only a processor upgrade if they decided to buy a better Intel processor. But if they choose to switch to AMD, they'll have to buy the mobo as well.So for *most* people, getting a Q9400 (or Q9550 if the prices drop) will cost around $270, while getting a Phenom II 940 will cost around $470. And since this is the case for the majority, I don't see Phenom II being price competitive at all.
RadnorHarkonnen - Thursday, January 8, 2009 - link
There are more people with AM2+ Motherboards than you can think of.They may not spew they writings on the forums or comment actively saying "I'm upgrading!!!".
Units shipped, i would say you r are really short sighted. And the AMD2/AMD3 compatibility is great.
KikassAssassin - Thursday, January 8, 2009 - link
Yeah, for people building new systems right now who don't want to spend the money on an expensive i7 mobo and DDR3, the Phenom II looks really nice. Intel probably isn't going to make any more LGA775 CPUs, whereas an AM2+ system might have more room for future upgrades with AM3 being backwards compatible.melgross - Thursday, January 8, 2009 - link
But if you do go the i7 route now, you won't have to upgrade for a longer time than if you go with Phenom 1. Overall costs over time will still be lower.melgross - Thursday, January 8, 2009 - link
Oops! meant Phenom 11, or course. Anyway, the higher performance vs the price is worthwhile for many people.plonk420 - Thursday, January 8, 2009 - link
ask Dark Shikari of x264 fame .. i'm sure he could tell you an approximation of Phenom's L3 cache latency... and possibly Phenom II latency soon.hameed - Thursday, January 8, 2009 - link
In the first table here http://www.anandtech.com/cpuchipsets/showdoc.aspx?...">http://www.anandtech.com/cpuchipsets/showdoc.aspx?... the percentages are hard to understand since they need to be flipped (i7 is before Quad) and btw in Cinebench the Quad advantage is 12.8% not 4.8% and the CS4 percentages are also not accurate.