Socket AM3 Arrives -- AMD Releases Five New CPUs that Support DDR3


Who says AMD moves too slowly? Just a month after releasing its well regarded Phenom II mid-range CPUs, the company is back with no fewer than five new P-II chips and its new AM3 socket that support DDR3. We give you the skinny on AMD’s latest quad and tri-cores and help you sort through AMD’s bewildering array of CPU choices.

War. What is it good for? Absolutely nothing. Well, except when it’s a CPU war. In that case, it’s good for consumers. Really good for us. With the unveiling of five new AMD’s latest Phenom II CPUs supporting DDR3, it’s pretty clear that the CPU war that started with the unveiling of the Phenom II in January is escalating.

AMD’s new lineup includes the 2.6GHz Phenom II X4 for $175, the 2.8GHz Phenom II X3 720 Black Edition at $145, and the 2.6GHz Phenom II X3 710 for $125. AMD’s two other new chips: the 2.6GHz Phenom II X4 910 and the 2.5GHz Phenom II X4 805. The 910 and 805 are OEM only CPUs and pricing was not released but you can expect that gray-markets will carry them and that the prices will follow the numbers. The 805, for example, should be slightly cheaper than the $175 810 and the 910 should be cheaper than the $195 Phenom II X4 920.

Lost in the numbers? So where we. AMD’s lineup is so bewildering to us today that we had build a spread sheet just to sort it out!

There are five prominent things to note with the new CPUs: They all support AM3, the HyperTransport speeds are higher, the L3 cache size is different, the tri-cores are back and the thermals are lower. We’ll address these in order.

AM3 socket

AM3 is AMD’s new socket standard that is built to support DDR3. The good news is that AM3 CPUs feature both DDR2 and DDR3 controllers. This means you can install an AM3 CPU in an AM2+ (and even some AM2) motherboards. You cannot, however, install an AM2+ CPU in an AM3 board. To prevent damage, the AM3 sockets have two fewer pins so you can’t even physically insert an AM2+ CPU in the socket. All Phenom II CPUs except for the two original launch CPUs should be AM3-based.

Can you spot the two fewer pins on the AM3 CPU on the right vs. the AM2+ CPU on the left?

Why didn’t AMD make the two original chips (the Phenom II X4 940 and 920) AM3 too? The company said it wanted to get them out as soon as possible and ditching AM3 support a cut quite a bit of engineering time off. We can understand that but it’s only been a month since the 940 and 920 were unveiled so couldn’t it have waited just a little longer so as not to confuse the hell out f people and piss off 940 and 920 owners? Apparently not. In fact, we’ve been told by AMD officials that the 940 and 920 actually had the AM3 controllers in them but they not turned on. If we ever get the time, we’ll have to snip the pins off a Socket AM2+ 920 and see what happens when it’s inserted into an AM3 motherboard.

HyperTransport Speeds

The newest Phenom II all sport 4GHz HyperTransport speeds. The original Phenom II X4 940 and 920 only ran at 3.6GHz HyperTransport speeds. Why? Again, AMD said it need to cut a few corners to get the 940 and 920 out as soon as possible and limiting the speeds to 3.6GHz help it do that. The company notes that it’s not like the CPUs are saturating the bandwidth anyway so it should have no real impact on performance. We, frankly, haven’t noticed that much of a difference either and we have to note that only the original Phenom X4 9950 and Phenom X4 8850 sported the 4GHz HyperTransport speeds. All others were lower.

If you’re really interested in how AMD’s Phenom’s look from an HT speed context here’s our chart sorted by HyperTransport speeds:


AMD is now also resorting to smaller cache versions to differentiate its models. This is an old technique long used by Intel and AMD and helps maximize the yields. If a CPU has a bit of defective cache, Intel or AMD turn off that portion and sell it as a lower model which is why these new chips often have the same die size as the larger L2/L3 chips. As the process matures and the yields get good enough that all of the cache is good, the companies have been known to actually produce smaller cache versions to even further maximize the yield. Generally, the largest cache models cost the most. For AMD’s Phenom II lineup, a 9XX denotes the larger 6MB L3, while an 8XX denotes 4MB of L3 cache.

Again, here’s the view of AMD’s Phenom CPUs from an L3 cache perspective:


Like the cache, AMD is also maximizing its yields by taking quad-core procs that have one bad core and selling them as tri-cores. Initially, enthusiasts scoffed at the idea of a quad-core minus one, but they’ve gradually been accepted. AMD has also had some success by putting the tri-cores against Intel’s dual cores. For the most part, three execution cores will indeed give you better performance in multi-threaded applications and multi-tasking than dual-cores. Here’s a break down of the X3’s by clock speed.


The final difference with these new chips is the thermal or TDP ratings. The original Phenom II X4 940 and 920 both had enthusiast-class TDP ratings of 125 watts. As more mainstream parts, all five new CPUs run are rated to disperse about 95 watts of heat under full load. It appears that AMD is now pushing 125 watts as its maximum TDP for desktop parts. Only one chip, the original Phenom X4 9950, hits 140 watts. All others are 125 watts or lower. Again, here’s a view from the TDP perspective.

We can’t touch on this CPU launch without tackling the big question: DDR3.

And you can’t tackle DDR3 without openly wondering why the hell is AMD so slow in adopting new memory standards? We find this to be especially ironic because it was AMD that made DDR what it is today.

Years ago, Intel decided that a fast, serialized, memory standard would benefit PCs. The solution to this was Rambus’ Direct RDRAM memory. Intel bet it all on RDRAM and restricted the Pentium 4’s chipsets to Direct RDRAM only. The problem is the RAM maker’s didn’t want RDRAM due to the licensing fees that they would have to pay Rambus. But what could they do if Intel made the CPUs and chipsets for it?

AMD saw it’s opening and led memory makers in a mutiny against Intel by supporting DDR with Athlon. The mutiny was successful, Direct RDRAM was tossed under the bus and Intel embraced DDR with a bear hug. Although we now believe the industry and the media (including Maximum PC) made a mistake by not moving to Direct RDRAM, or at least, something similar to it, DDR was the standard.

So how the hell did AMD turn from the darling of the memory industry into a perceived drag ass? DDR2 was adopted by Intel two years before AMD introduced AM2. And Intel’s DDR3 chipset has been around since late 2007.

We’ve long had a pet theory that moving the memory controller into the CPU has taken some flexibility out of memory choices. The original Athlon 64 was hard wired to only run DDR. Likewise, AM2 Athlon 64s and Phenoms could only run DDR2. AMD’s solution to supporting both DDR2 and DDR3 is to build a memory controller that supports both types of RAM into the AM3 procs.

AMD’s official explanation for its seemingly slow memory updates is that it only adopts new memory standards when its cost effective and when people actually want it. Hence, even with AM3, the company is still pooh poohing DDR3. AMD says it still believes the vast majority would rather have the cost savings of DDR2 over DDR3.

DDR2’s cost performance over DDR3 isn’t what it once was though. A year ago, 2GB of DDR3 would fetch several hundred dollars. Today, you can buy 4GB of Crucial DDR3/1066 for $79. Change your selection to 4GB of Crucial DDR2/800 and it would cost you $38. So DDR2 does cost 100 percent more, but we’re talking 80 bucks here folks for 4GB of RAM.

Finally there’s price.

AMD’s pricing on its CPUs has been a great deal for consumers. It is a bit confusing though. At first glance, you’d think it was 22 CPUs spread out in a price band from $225 to $101. But two of those chips are OEM only. Another four are aimed at servers and media center PCs and another four are for business desktops.


How we tested

We used an MSI DKA790GX board outfitted with 4GB of Patriot DDR2/1066, a PC Power and Cooling 1200 Watt PSU, a GeForce 8800GTX and 150GB WD Raptor drive to test the three AMD procs. As a comparison, we used a 2.83GHz Core 2 Quad Q9550 in a Gigabyte GA-X48-GQ6 with 4GB of DDR3/1333 with a WD Raptor 150 and GeForce 8800GTX. For the Core i7-920, we used an Intel DX58SO with 3GB of DDR3/1066, GeForce 8800GTX and WD Raptor 150 drive. All configurations used Windows Vista Home Premium in 64-bit flavor.

The results were mostly what we expected. Performance against its sibling, the 3GHz Phenom II X4 940 was what you would think a CPU with 400MHz fewer clock cycles would score. We did see some unexpected results though. The AM3 Phenom II X4 810 part slightly outscored the Phenom II X4 940 in several of the memory benchmarks. We didn’t expect this given that we were running it in the same board with the same RAM and with same RAM speeds and timing set. This is either a hiccup in our test or an errant setting from our earlier test of the 940. We unfortunately didn’t have time to go back and rerun our tests with the 940. It is also possible that AMD has taken the extra few months it had with the newer AM3 parts to tweak the memory controller.

Between the Intel and AMD chips there was no comparison but that’s no surprise. AMD doesn’t expect the 810 to take on the 2.83GHz Core 2 Quad Q9550. Instead, AMD believes the CPU is better matched against the budget 2.33GHz Core 2 Quad Q8200 part. The $163 Q8200 has 2MB less L2 cache than the Q9550 and runs about 500MHz slower. We didn’t have Intel’s ultra budget part handy to test but subtract 500MHz from the Q9550’s scores and take away a small bit for the cache and both parts are likely competitive with each other.

The $284 Core i7-920, of course, is the fastest of the bunch but it’s also more expensive to buy and build a machine around.
Realistically, this comes down to Phenom II vs. Core 2. There, it’s a competitive crowd as Intel has as many or more CPUs than AMD does. There is only one advantage an AMD builder would have over an Intel machine: future upgrades.

Intel is pretty set to push the superior performing Core i7 as the platform of the future and is unlikely to spend the money and engineering to say, qualify a 3.5GHz CPU for the Core 2 platform. AMD, on the other hand, is committed to AM3 for now. That means it’s possible we’ll see a 3.4GHz or 3.6GHz Phenom II down the road. And even if that chip comes out in AM3 the backwards compatibility with AM2+ means those people won’t get left behind either.

While Core 2 Quad certainly has some legs left in it, those with an eye towards future upgrades should look to Core i7 if they want performance. And if they just want a good performing budget chip, AMD’s Phenom II is actually looking like a more stable platform over Core 2 right now. We’re not at all saying that Core 2 is dead, especially since in many ways, it still far outperforms all of AMD’s CPUs, but in six or nine months, Core 2 will feel stale as only Core i7 and Phenom II will get performance upgrades.

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