We summarized below all CPUs included in this review with their main specs.

CPU	Cores	Internal Clock	External Clock	L2 Memory Cache	Platform	TDP
Athlon 64 3800+	1	2.4 GHz	*	512 KB	Socket 939 (DDR)	89 W
Athlon 64 X2 4600+	2	2.4 GHz	*	512 KB x 2	Socket 939 (DDR)	110 W
Athlon 64 X2 5000+	2	2.6 GHz	*	512 KB x 2	Socket AM2 (DDR2)	89 W
Athlon 64 FX-60	2	2.6 GHz	*	1 MB x 2	Socket 939 (DDR)	110 W
Athlon 64 FX-62	2	2.8 GHz	*	1 MB x 2	Socket AM2 (DDR2)	125 W
Pentium 4 550	1	3.4 GHz	800 MHz (200 MHz x 4)	1 MB	Socket 775 (DDR2)	115 W
Core 2 Duo E6700	2	2.66 GHz	1,066 MHz (266 MHz x 4)	4 MB	Socket 775 (DDR2)	65 W
Core 2 Extreme X6800	2	2.93 GHz	1,066 MHz (266 MHz x 4)	4 MB	Socket 775 (DDR2)	75 W

* Since AMD64 CPUs have their memory controller embedded in the CPU, the datapath between the CPU and the memory controller uses the CPU internal clock rate instead of an external clock rate as it happens on Intel CPUs. To communicate with components outside the CPU, AMD64 CPUs have two busses, the memory bus and the HyperTransport bus. The memory bus run up to DDR400 or DDR2-800 depending on the platform (socket 939 or socket AM2, respectively) and the HyperTransport bus of the listed CPUs works at 1,000 MHz transferring two 16-bit data per clock cycle (also labeled as “2,000 MHz”), achieving a 4,000 MB/s transfer rate on each direction. A 800 MHz external bus on Intel CPUs can provide a maximum theoretical transfer rate of 6,400 MB/s while a 1,066 MHz external bus can provide up to 8,528 MB/s. Direct comparison of this particular spec between Intel and AMD CPUs is really tricky as Intel external bus is used for both accessing the main RAM memory and other components – the video card in particular –, while on AMD64 CPUs two separated paths are used. Also, on Intel CPUs the same datapath is used for transferring data in and out, while HyperTransport bus provides two separated paths for input and output.

Thanks to Core microarchitecture –an enhancement over Pentium M’s – Core 2 family dissipates a lot less power, meaning less heat (TDP stands for Thermal Design Power). As you can see on the table above, Core 2 Duo and Core 2 Extreme dissipate less power than all other CPUs included in our review. It is amazing to see how a dual-core CPU, which has two complete CPUs inside, can dissipate less power than a single-core Pentium 4. You can claim that they run at lower clock rates, however keep in mind that they have four times the amount of memory cache found on Pentium 4, which by itself would increase the CPU power dissipation a lot.

Unfortunately Intel didn’t provide us Pentium D and Pentium Extreme Edition samples for reviewing. A pity.