Processor

The processor is the main part of the computer. You might say it is the brain or the heart of a computer. Today’s PCs use CPUs made by two main companies

• Intel (Pentium, Celeron, Pentium II, Pentium 4, Pentium D, Pentium Core 2 Duo and Quad Core),
• Advance Micro Devices or AMD (K6, Athlon, Athlon XP, Athlon X2

INTERNAL CLOCK SPEED: CPUs or processors are often graded by their internal clock speed. This speed is the number of operations a processor can perform per second. For example, the Pentium-4 3.0 GHz has a clock speed of 3000 KHz or 3.0 GHz.

EXTERNAL CLOCK SPEED: This is the speed with which the CPU can communicate the rest of the system. The CPU communicates with the rest of the system via a gateway called system bus or front side bus. Hence, the external clock speed is also called Front Side Bus (FSB) speed.

MEMORY CLOCK SPEED: This is the speed with which the RAM is given requests for data.In old CPUs, the memory clock speed used to be the same as the FSB.

With the Athlon K7 processor, AMD introduced something new. The Athlon processor had an FSB of 100 MHz but the bus could make 2 data fetches per cycle from the RAM. So, the effective rate became 200 MHz. AMD then went on to claim that the Athlon had an FSB of 200 MHz. AMD called this Double Data Rate (DDR) FSB.

Intel later introduced this feature in their first Pentium-4 processor. In the P-4 processor, the system clock operated at 100 MHz and the bus was sampled 4 times, which resulted in the FSB being touted as 400 MHz (100 x4). Intel called this Quad-Pumped Bus. As of December 2006, external frequencies were at 200 MHz and Intel has been touting a FSB speed of 800 MHz for their processors.

Both Intel and AMD advertised their memory clock speed as the FSB of their processors. The correct FSB measure would have been the external processor frequency, as few components other than the RAM can operate at such high frequencies.

AMD later introduced a technology called HyperTransport, which integrated the memory controller in the CPU itself, thus eliminating the Front Side Bus (FSB)! This is a radical change in PC architecture because now the CPU could directly handle RAM operations and was not limited by an FSB. The PC architecture was also significantly changed with the HyperTransport Graphics Tunnel replacing the North Bridge and the HyperTransport I/O Bus Tunnel replacing the South Bridge. See the graphic below. With HyperTransport, all data is sent in packets instead of the earlier inefficient scheme of reserving bandwidth streams. HyperTransport’s optimum use of bandwidth results in higher throughputs. Because of the parallel nature of HyperTransport, it initially operated at 1 GHz. Now, it works at a speed of 2 GHz. Despite the obvious advantage of HyperTransport technology, Intel continues to use its dated FSB-based architecture and makes inefficient CPUs.