As we have already said, the two processors used on Quad FX platform are interconnected using a HyperTransport bus. Because of that, a CPU to be compatible with Quad FX platform would need at least two HyperTransport busses: one for interconnecting the two CPUs and another to connect the CPU to the chipset. As Athlon 64 FX based on socket AM2 have only one HyperTransport bus, AMD had to launch a new version of Athlon 64 FX processors for Quad FX platform. These new Athlon FX models start with the number 7 and three models were released so far: FX-70, FX-72 and FX-74. These new processors use the new socket F (1,207 pins) pinout, which was originally targeted to the new Opteron processors, and three HyperTransport busses. The main technical specs of these new processors are:

• Dual-core technology
• 128 KB L1 cache (64 KB for data + 64 KB for instructions) per core
• 1 MB L2 cache per core
• 90 nm manufacturing process
• Socket F (1,207 pin)
• DDR2 memory controller supporting DDR2-533/667/800 under dual channel mode
• Three HyperTransport busses working at 1 GHz (4 GB/s) each. This clock can also be referred as “2.000 MHz”

On the table below you can see the details of the Athlon 64 FX-7x released so far.

OPN (Tray)	OPN (Box)	Model	Clock	TDP	Max. Temp. (ºC)	Voltage
ADAFX74GAA6DI	ADAFX74DIBOX	FX-74	3 GHz	125 W	56	1.35 V - 1.40V
ADAFX72GAA6DI	ADAFX72DIBOX	FX-72	2.8 GHz	125 W	63	1.35 V - 1.40V
ADAFX70GAA6DI	ADAFX70DIBOX	FX-70	2.6 GHz	125 W	63	1.35 V - 1.40V

You will have two buy two identical processors to use them on Quad FX platform. You cannot use an Athlon 64 FX-74 together with an Athlon 64 FX-70 on the same motherboard, for example.

Regarding the RAM memory, as we explained on the previous page, each processor controls its own RAM memory. Thus in order to configure dual channel mode correctly on the platform you will need at least four identical memory modules (two for each CPU) and not two as usual (in fact this is another reason this platform is called Quad FX or “4x4” as it was called before its official release). In theory the installation of more RAM memory would be done in multiples of four modules, but the reference motherboard for this platform has only four memory sockets.

Also, the memory controller found on Athlon 64 FX-7x CPUs support a technology called NUMA (Non-Unified Memory Architecture), which allows one processor to access the memory controlled by the other processor thru the coherent HyperTransport bus that interconnects the two CPUs. The difference between a coherent HyperTransport bus and a regular HyperTransport bus is exactly the ability of carrying memory information by the former.

The rest of the features found on Quad FX platform isn’t set by the processors but by the chipset. Let’s talk about it.