Features and overclocking

As we just mentioned, the Athlon 64 FX-70 shares all the key specs found in the rest of the Quad FX platform yet it costs significantly less.

If you recall, the Quad FX processors are based around AMD’s new 1207-pin socket dubbed Socket F (ASUS refers to it as Socket L1). With the debut of the new socket, AMD now uses organic land-grid array packaging and the pins are now located on the motherboard itself rather than the underside of the processor. This makes processor installation a lot easier, as you no longer have to worry about bent pins on the processor.

Fundamentally the new Quad FX processors are based on AMD’s Opteron architecture. Like AMD’s Opteron processors, each FX CPU has its own dedicated dual-channel memory interface, with two DIMM slots associated with each processor. This gives the quad FX platform twice the memory bandwidth of AMD’s AM2 platform, 12.8GB/sec peak memory bandwidth on an AM2 Athlon 64 FX-62 system versus 25.6GB/sec for FX-70. As a result, total system bandwidth goes from 20.8GB/sec on AM2 to 33.6GB/sec for a quad FX processor like the FX-70.

Of course, here we should remind you that in order to take advantage of this, you’ll need to populate all four DIMM slots with memory, otherwise the system will run in single-channel memory mode, resulting in slower performance. Also like Opteron, 4x4 systems also follow a non-uniform memory access model (NUMA), so you’ll need a NUMA-aware OS such as newer Linux builds, Windows Server 2003 64-bit Edition, or Windows Vista.

One key difference between the latest FX processors and Opteron however is that the FX CPUs support conventional, unbuffered, non-ECC memory. This means you can use the same off-the-shelf DDR2-800 or DDR2-667 memory already used for AM2 on the new FX CPUs.

This table sums up the Quad FX CPU lineup as it stands now:

AMD's Quad FX Lineup
CPU	L1 Cache	L2 Cache	Clock Speed	Price
Athlon 64 FX-74	128KB+128KB	2x1MB	3.0GHz	$999 Per Pair
Athlon 64 FX-72	128KB+128KB	2x1MB	2.8GHz	$799 Per Pair
Athlon 64 FX-70	128KB+128KB	2x1MB	2.6GHz	$599 Per Pair

Taking the FX-70 beyond 2.6GHz

Despite the efforts of a handful of other manufacturers, dual CPU overclocking has never truly taken off in the mainstream segment. Arguably the best attempt came from Abit way back in 1999 with their BP6 motherboard. One popular solution was to overclock two Celeron 366 processors to 550MHz, giving end users high-end performance at a fraction of the cost of using dual Pentium III or Xeon processors, but dual CPU overclocking on the AMD platform hasn’t been truly viable for one reason or another up until now.

With NVIDIA’s new nForce 680a chipset and the Quad FX platform, AMD enthusiasts finally have a dual-processing platform that they can truly with when it comes to overclocking.

It all starts with the ASUS L1N64-SLI WS motherboard, which is the only nForce 680a board on the market at this point. The L1N64-SLI WS is one extremely high-end motherboard, featuring four PCI Express graphics slots for expansion: three of the four graphics slots have enough room for dual-slot graphics cards like the GeForce 8800 GTS/GTX. The board even has a whopping 12 SATA ports!

Out-of-the-box the L1N64-SLI WS supports up to 10 USB ports, although the chipset can natively drive another 10 USBs with additional headers, and dual GigE Ethernet connections. The board is cooled entirely passively using an array of copper heatsinks and heat pipes to cool the chipset and VRM circuitry. This allows the motherboard to generate no noise, but we highly suggest you use the supplemental external fans ASUS provides if you intend to overclock your system.

For overclocking, the L1N64-SLI WS offers HyperTransport speeds up to 400MHz in 1MHz increments, and memory speeds of 400, 533, 667, and 800MHz. CPU voltages up to 1.40V are also provided in BIOS with an additional 200mV provided via the CPU vcore over-voltage BIOS setting, while memory voltages top out at 2.5V and HyperTransport voltages at 1.4V.

CPU over-voltage option

1.4V max in current BIOS

Keep in mind that the L1N64-SLI WS is an extended ATX form factor motherboard, so you’ll need a large case in order to house it.

In order to keep the FX-70 processors as cool as possible for our overclocking endeavors, we decided to skip the stock AMD heatsink/fan units, opting instead to use a pair of Zalman CNPS9700 coolers. At stock speeds, we noted idle temps that were about 10 degrees Celsius cooler as a result of using the Zalman coolers, with the processor running around 31-35 degrees Celsius.

Size comparison between the CNPS 9500 (left) and 9700 (right)

The CNPS9700s aren’t officially on the list of approved Socket F coolers, but they mounted on the board just fine, although it was a very tight fit. In hindsight the CNPS 9500 is a little smaller and probably would have been easier to install because of this, but oh well, we were happy with our OC’ing results:

CPU1 Overclocked

CPU2 Overclocked

We were able to overclock the FX-70’s to 3.12GHz (15.0x208). In order to get there we had to use the vcore over-voltage setting, which was set at the max setting of 200mV. We were actually able to boot up to much higher speeds, the CPU ran up to 3.2GHz with no problems. At that speed the system would boot as far as the Windows XP splash screen; at that point, the system wouldn’t lock up, but it wouldn’t boot into Windows either. It literally just sat there as if it wasn’t sure if it wanted to boot or not, with the HDD occasionally being accessed.

Because of this, we think we could have pushed the CPU further with a little more voltage. In fact, ASUS’ initial BIOS provided more CPU voltage options and we’ve asked ASUS if perhaps they’ll reconsider and integrate more voltage settings for the CPU. We’ll be keeping an eye on this to see if anything develops.

So how does the FX-70 perform in comparison to the other quad-core CPUs at 3.19GHz? Let’s find out!