AMD Creates Two-Socket Athlon FX Variant, Demos Quad-Core Opteron

Published: December 6, 2006

by Timothy Prickett Morgan

Chip maker Advanced Micro Devices last week announced part of its answer to rival Intel's launch three weeks ago of quad-core chip modules, branded the "Clovertown" Xeon 5300s for entry servers and the "Kentsfield" Core 2 Extreme for high-end PCs. AMD did not deliver a quasi-quad core chip, like Intel did, based on the AMD 64 cores, but rather did a variant of what high-end PC buyers have already been doing: building two-socket machines based on Opterons.

And, just to make sure that everyone knows that AMD is still working on delivering a real quad-core chip, code-named "Barcelona," AMD picked this same day to tell the world a little more about this chip and to demonstrate that it is actually working in a four-socket server box. The quad-core Barcelona will be brought to market in Athlon 64 FX and Opteron Rev F sockets.

Intel's Clovertown and Kentsfield chips as well as IBM's Power5+ quad core modules puts two chips, side by side, into a single package that allows them to be plugged into a single CPU socket. They share the same chip buses, but in general, by taking this quasi-quad core approach, Intel and IBM can deliver from 50 percent to 60 percent more performance in a box. AMD could have, conceptually at least, done the same thing with its "Santa Rosa" Rev F Opterons, which were announced in the summer. But AMD believes that it needs to deliver a true quad-core chip with an integrated L3 cache to wring the absolute highest performance out of the AMD 64 cores in its chips.

Still, among high-end PC gamers, AMD wants to have something to sell against the Kentsfield quasi-quads. And that is what the AMD Quad FX platform is all about. And while this platform is ready for the Barcelona variants that will have the Athlon FX brand, don't be confused. AMD is not delivering a quad-core Athlon 64 FX at this point. Rather, it is delivering the first two-socket platform that supports the Athlon 64 FX processor, which is the high-end implementation of its desktop Athlon chip.

In a normal Athlon 64 FX chip, the HyperTransport links that allow NUMA clustering of processors (which means the chips have cache coherent memory and can share a single copy of an operating system) are deactivated. With the Quad FX platform, AMD turns these links on. One set of coherent HyperTransport links is used to link the two sockets on the motherboard and to allow all four processor cores on the machine to access the DDR2 main memory that is attached to both sockets. That is simple enough. But just to get a little crazy, rather than have a single chipset hanging off the HyperTransport to manage peripherals, the Quad FX platform has two nVidia nForce 680a chipsets. This means a single Quad FX motherboard can have four PCI Express x16 slots, which can drive four separate video cards. The board also has a single ATA slot, a dozen SATA-II disk ports, eight USB ports, two Gigabit Ethernet ports, a PCI slot, and a PCI Express x1 slot. The Quad FX board also has four DDR2 main memory slots (which means it should support up to 8 GB using the 2 GB DIMMs that are within the price range of gamers) and an integrated RAID 0/1/5 disk controller.

The Quad FX board will support Linux and Windows XP Pro, which has support for the AMD Opteron (which is what this Athlon FX really is) as well as for two-socket NUMA processing. Only the top-end Windows Vista Ultimate version will run on this box, however, since the other Vista variants will only work on single-socket PCs and workstations.

The first vendor to implement a Quad FX board is Asustek Computer, and that board is the L1N64-SLI motherboard; it is expected to retail for between $300 and $350. In benchmark tests against a single-socket Athlon 64 FX-62 platform based on the Asustek M2N32SLID motherboard, the Quad FX platform delivered from 50 percent to 80 percent more oomph on a variety of workloads. It is reasonable to assume that with a two quad-core Barcelona variants, this machine will be able to push another 50 percent or more work out--and in the same thermal envelope. Desktop Athlon FX variants of the Barcelona chip are expected in the second half of 2007.

And, as Ian McNaughton, product manager of the Athlon 64 FX product line, it is important to note that the reference platform uses a chipset from nVidia, the main rival to ATI Technologies, which AMD acquired this summer. "Whether or not we use ATI or nVidia or other chipsets will be based on performance," explains McNaughton. "We will choose the best products for our customers."

There are three Athlon 64 FX processors that can be plugged into the Quad FX platform, and AMD is selling them in pairs only. They are all implemented in 90 nanometer processes, they all have 1 MB caches per core, and they all have a thermal design point (TDP) of 125 watts. The FX-70 chip runs at 2.6 GHz and costs $599 per pair; the FX-72 runs at 2.8 GHz and costs $799 per pair; and the FX-74 runs at 3 GHz and costs $999 per pair.

With the top-end Athlon 64 FX-74, 4 GB of memory, all 12 disk drives, and four video cards, McNaughton says that such a machine could keep all of its parts whirring using an 850 watt power supply and still have some room left over. In tests at AMD's labs--which did not stress all the video cards and drives to their maximum--the highest power that the Quad FX platform drew was around 740 watts.

While this board was not designed as a server board, two dual-core Athlon 64 FX processors and a dozen SATA ports would make it a very respectable entry server--an idea that McNaughton found laughable.

The future quad-core Barcelona Rev F chip in a server is, of course, not laughable, and it would be nice if they were here before the middle of next year. But, the Barcelonas--or at least four of them--are out of the labs and were demonstrated running Windows Server 2003 in a four-socket, 16-core server by AMD.

According to John Fruehe, worldwide market development manager for server and workstation products at AMD, the quad-core Barcelona chips will be delivered in the same thermal envelopes as the dual-core Santa Rosa Opterons. But there are some differences. While some of the dual-core Santa Rosa had 1 MB of L2 cache per core, the cores in the Barcelona chips will only have 512 KB of L2 cache per core. You might think that the lower cache would be a hit on performance, but the Barcelona chip also includes an on-chip, shared L3 cache memory that is 2 MB in size. This L3 cache will be a significant enhancer to performance. The doubling of cores and the addition of L3 cache is all enabled by the move from 90 nanometer to 65 nanometer chip making processes.

Fruehe will not talk about clock speeds on the Barcelona chips, but says that AMD can deliver more than 50 percent better performance compared to the Santa Rosa chips within the same thermals; exactly how much more, no one is saying.

The Barcelonas will come in mainstream versions with a 95 watt TDP, plus the Opteron SE variant, which clocks higher and has a 120 watt TDP. There will also be Opteron HE variants, which run at the same clock speeds as the mainstream parts, but which run using lower voltages and therefore have a 68 watt TDP.

The Opteron 8000 series, which go into four-socket and larger servers, will get the Barcelonas first, followed by the two-socket Opteron 2000 series, and then later in 2007, the single-socket Opteron 1000 series and, presumably, the Athlon 64 FX and Althon 64 X4.

"We really think that the sweet spot for Barcelona is four-socket machines, since these boxes have the kinds of workloads that can take the best advantage of threads and cores" says Fruehe.

As for pricing on the Barcelona Opterons, Fruehe is not giving away any secrets--except to say that AMD will "price to value." As for Intel pricing its Clovertons at the same points as the "Woodcrest" dual-core Xeon 5100s, he said that "Clovertown" has a fairly low price, which he thinks reflects its value." What he also said when pressed is that the performance of the Opteron line will go up dramatically with the Barcelonas and that the price/performance would come down.

Early next year, AMD will raise the curtain a little higher on the Barcelona chips, talking a little more about performance, features, power consumption.

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