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Review: AMD Socket AM2: Athlon 64 FX-62 and nForce5 590 SLI

by Ryszard Sommefeldt on 23 May 2006, 05:00


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AMD Socket AM2

New CPU sockets and platform shifts are a necessary evil. On the one hand, depending on the type of PC user you are and how often you upgrade, it's what facilitates a larger-than-normal expenditure as you buy in all the other new components the new socket and platform seek to enable. The flipside of the coin is that very enabling; the new socket and platform will advance things along in terms of technology support and performance, allowing the PC to do its thing and continue evolving.

AM2, as you'll be well aware by now, is one such socket and platform shift. To get AM2 is to first understand that a modern Socket 939 system is one that carries K8 core microprocessors with integrated DDR memory controller, PCI Express (an inflection point brought about mostly by nForce4) as the dominant peripheral interconnect and a modern I/O processor.

AM2, in those terms, is the integration of a DDR2 memory controller with a K8 microprocessor, rather than DDR, keeping the same PCI Express interconnect base and a modern I/O processor to (mostly) do the rest.

At least that's the case initially, AMD pointing out that AM2 has legs for at least two years from now and AMD planning an architecture change before those two years run out. More on that concept a bit later.

Socket AM2 is pin-based like Socket 939, and carries the same 940 pins as, well, Socket 940. That's not to say the pin layout and electrical requirements are the same as the current Opteron (and one time desktop Athlon 64 FX) socket. AM2 changes the pin layout so that current Socket 940 processor packages don't fit, and it also brings with it new power requirements for its CPUs, and of course new trace routes for the new memory standard it supports.

Socket 940, Socket 939 and Socket AM2 all look very much alike. Here's AM2 in pictures.


Pictured on an ASUS M2N32-SLI Deluxe (revision 1.02G, more on which later), the AM2 socket looks as Socket 939 does. The giveaway, should spotting pin locations not be your thing, is the quartet of DDR2 memory sockets above the socket area.

The retention bracket for AM2 coolers is changed, too, four screws used to attach to the backplate on the rear of the board. That said, coolers usable on Socket 939 (and indeed 940 and 754) should be usable without any changes on Socket AM2 boards. Got a decent aftermarket cooler for your 939 box and want to take it with you to AM2? That's just fine.

Electrically, AM2 is paired with a tweaked VRM specification which regulates voltage supply to the CPU and memory, versus what was specced for Socket 939. A board level change for vendors to implement, it means AM2 mainboards should support all the launch AM2 processors (of which there's many) and CPUs that'll use the socket in the future.

AMD are happy to state that due to the use of HyperTransport for connecting the CPU to the rest of the system, board designs for Socket AM2 can be based on existing Socket 939 designs with literally not much more than board routing and placement for the DDR2 DIMM sockets and the new retention mechanism. It's just a tracing problem to solve then, in the main anyway.

All that means that thinking of it as Socket 939 with DDR2 is no bad thing, since that's mostly what's changed.

CPU Range

Until today, high-end Athlon 64 sat on a separate socket to low-end AMD Sempron. AM2 changes that, allowing all desktop consumer processors to place their new 940 pins into the same socket, from Sempron through Athlon 64, all the way up to Athlon 64 X2 and Athlon 64 FX.

Launch day therefore brings CPUs with all four monikers, available for sale today to place into the myriad boards supporting AM2 and DDR2 with supporting core logic.

Not only that but AMD are also offering different power grades of certain AM2 CPU SKUs, much like they do with Opteron, Opteron HE and Opteron EE. Called EE and EE SFF (small form factor), AMD have graded those according to maximum TDP.

CPU SKU Possible TDPs
AMD Athlon 64 FX 125W
AMD Athlon 64 X2 89W, 65W, 35W
AMD Athlon 64 62W, 35W
AMD Sempron 62W, 35W

You can see some common TDPs across processor range, Athlon 64 X2, Athlon 64 and Sempron all sharing a 35W TDP for some CPUs in the range, for example.

As far as on-the-box branding goes, take the three versions of Athlon 64 X2 3800+ that AMD will offer:

AMD Athlon 64 X2 3800+, 89W
AMD Athlon 64 X2 3800+ EE, 65W
AMD Athlon 64 X2 3800+ EE SFF, 35W

So AMD will offer CPUs with the same performance but differing thermal outputs, allowing you to choose the version you need for the system form factor and cooling solution you want to use.

As far as launch processors go, it's pretty easy to get. Take everything that's available on 939 or 754 and it's also now available on Socket AM2 at the same clock rates and cache sizes, with the same ratings.

That's apart from Athlon 64 FX, where the FX-60 on Socket 939 makes way for a faster clocked FX-62 (of course). To add to that there's also a new X2 called Athlon 64 X2 5000+, sitting just above the old X2 4800+ on 939.

So a brand new X2 and a replacement FX, to go with everything else available on the old sockets, giving you plenty of choice on AM2 from the very beginning.

Of course they're facilitated by new core revisions for each bit of base silicon that powers a CPU SKU. It's worth talking about those on a new page, letting me refresh your memory about what K8 is as a microprocessor architecture in the process. So let's talk K8 and new core revisions for AM2.