AMD Does DDR3 - The AM3 Phenom II


DDR3 at Last

DDR3 at Last

It has been a difficult time for both AMD and Intel, affected as they are by falling demand resulting from the current economic 'gloom and doom'. Intel reported dismal revenues for the last quarter while the new year has begun with more job cuts at AMD. The situation looks more bleak for AMD, as they have been hemorrhaging even before the economic downturn. Hence, there was a lot at stake here for AMD's recent 45nm shrink of its Phenom CPU microarchitecture, dubbed the Phenom II.

Fortunately, our last encounter with the Phenom II gave us a few reasons to be optimistic. The die shrunk has brought a larger L3 cache to a chip which runs cooler and is energy efficient than the original while at the same time boasting higher clock speeds. A lower total cost of entry for the entire platform (dubbed the Dragon) thanks in part to its use of DDR2 memory and a simple drop-in CPU upgrade for existing Phenom users helped to fuel this mainstream value perception. For enthusiasts, the return of some overclocking potential to the AMD platform is also much appreciated.

Yet this is but the beginning. Today, AMD launches its AM3 socket (938-pin) Phenom II, the first processors from the company to embrace DDR3 memory. It's a long awaited shift, coming more than a year after Intel made its move. However, with the AMD architecture having an integrated memory controller as it has been for a while now, one could argue that Intel only made its shift with its Core i7 architecture. In any case, there are up to five new 45nm AM3 Phenom II processors launched today, including the first triple-core Phenom II models.

Of these five models, three will be available in retail while the other two are tray versions for the OEM market. While the underlying architecture and process technology is similar to the earlier Phenom II models, there are some differences, chief being naturally the DDR3 support in the integrated memory controller. According to AMD, these AM3 processors can accept either up to DDR2-1066 or DDR3-1333. Hence you could drop them into an AM2+ motherboard and they will work fine, with a BIOS update at most. If you do plan to go DDR3, motherboard vendors have already released AM3 boards.

One thing about DDR3-1333 - the integrated memory controller on current AM3 processors only support a single DDR3-1333 DIMM per channel, thus limiting the amount of DDR3 memory that can feasibly be installed (good luck finding a 4GB DDR3 module now), even if the CPU does support up to 8GB memory on paper. At the moment, fully populating all the available DDR3 DIMM slots, assuming the typical 4 DIMMs, will result in a lower (than DDR3-1333) memory frequency.

One difference with these new models is that some of them (X4 810 and X4 805) come with only 4MB of L3 cache. If you remember, the Phenom II models that have debuted have 6MB of L3 cache and this is significant performance-wise compared to the original Phenom processors that have only 2MB of L3. No doubt, AMD has its sights on the mainstream segment with these 4MB L3 processors. The 2.6GHz Phenom II X4 810 in particular, is aimed at Intel's newer mainstream quad-cores, like the 2.33Ghz Q8200 with a 4MB L2 cache. Interestingly, the memory controller and HyperTransport on these AM3 Phenom IIs are running at 2.0GHz, faster than the 1.8GHz found on the Phenom II 940 and 920.

Finally, all these new AM3 Phenom II are 95W models, which are about 30W lower than the 125W models that have been launched previously. Thus, we're looking forward to better idle and peak power consumption numbers from these newcomers and to help us find out how they fare, AMD sent us two of the retail models, the Phenom II X4 810 and the Phenom II X3 720 'Black Edition'.

New AM3 Phenom II Processors
Processor Model Clock Speed L2 Cache L3 Cache HyperTransport Bus Memory Controller Speed Max TDP (W) Retail Price (US$) Availability
Phenom II X4 810 2.6GHz 512KB x 4 4MB 2.0GHz 2.0GHz 95 $175 Now (PiB)
Phenom II X3 720 'Black Edition' 2.8GHz 512KB x 3 6MB 2.0GHz 2.0GHz 95 $145 Now (PiB)
Phenom II X3 710 2.6GHz 512KB x 3 6MB 2.0GHz 2.0GHz 95 $125 Now (PiB)
Phenom II X4 910 2.6GHz 512KB x 4 6MB 2.0GHz 2.0GHz 95 N.A Now (Tray)
Phenom II X4 805 2.5GHz 512KB x 4 4MB 2.0GHz 2.0GHz 95 N.A Now (Tray)
Existing AM2+ Phenom II Processors
Phenom II X4 940 3.0GHz 512KB x 4 6MB 1.8GHz 1.8GHz 125 $229 Now (PiB)
Phenom II X4 920 2.8GHz 512KB x 4 6MB 1.8GHz 1.8GHz 125 $189 Now (PiB)