The CPU or Central Processing Unit is the brain of the computer and perhaps the most important part that determines system performance. Its function is to interpret and execute instructions and data contained in a software program. Intel is the leading CPU manufacturer today and the first one that introduced it in the market. The first to come out was the 8080 in 1974 followed by the 8088 in 1979. The following years saw the development of the other models like the 80286, 80386, 80486 and the Pentium series.  

At present, Intel have several different microprocessor product lines today: Pentium 4 and Pentium D (dual-core) for the mainstream segment, Celeron D for budget and entry-level users and Core 2 Extreme and Pentium Extreme for high-end users and enthusiasts.

AMD or Advanced Micro Devices is the only competition but is settled at second place.  It also offers several processor product lines like the most popular Athlon 64 that is intended for the mainstream segment.  The Sempron is for budget and entry-level users, the Athlon 64 FX for high-end users and gamers, and the new Athlon 64 X2 for more demanding applications.

With so many microprocessors currently available in the market today, a user might be at a lost which one to choose for his particular requirement.  In the selection process, it is important to understand the different CPU specs that have something to do with their performance.

CPU Speed

The CPU speed is a measure of how fast instructions and data signals can move in various branches of a CPU's many circuits.  The megahertz or MHz, a unit of alternating current (AC) or electromagnetic (EM) wave frequency is used to express microprocessor clock speed. The unit is also used in measuring bandwidths for high-speed digital data signals. Newer processors released are actually in the gigahertz GHz range. 1 MHz is equal to 1,000,000 cycles per second while 1 GHz is equal to 1,000,000,000 cycles per second. Take note that the faster the CPU speed, the faster the computer will process information.

Front Side Bus

FSB or Front Side Bus connects the CPU to the main memory (RAM) and other components within the computer.  The FSB of a computer can vary in speeds from 66MHz to 800MHz and beyond.  Aside from the CPU speed, it is also an important feature to look at when purchasing a new computer.  The Intel Celerons for example have FSBs starting at 66Mhz.  That for the Pentium IV class is at 800Mhz, while for AMD’s Athlon XP class, it tops out at 333Mhz.  As in the case of the CPU speed, the faster the FSB, the faster the computer will process information.

Cache

Cache refers to a special high-speed memory mechanism that stores the most frequently used data or instructions that a CPU processes. By keeping as much of this type of information in the faster cache memory of the CPU, it prevents the CPU from having to access directly the slower computer DRAM memory.  This way, the CPU speed is not limited by the slower connection between the CPU and memory and other peripheral components.

Another issue to look at is the tradeoff between cache latency and hit rate. Larger caches have better hit rates but have longer latency. To resolve this problem, the use of multiple levels of cache was developed (level 1, level 2 and level 3).

Hyper Transport

HyperTransport was developed to replace the front-side bus, in which there is no standard among different types of machine.  In order to interconnect proprietary front-side buses to standard buses like the PCI Express and the AGP, adapters may be required.  To remedy this, HyperTransport, which is an open specification standard was developed so a compliant device will work with HyperTransport enabled microprocessors.

Hyper-Threading

Hyper-threading is Intel's proprietary technology for simultaneous multithreading implementation in their Pentium 4, Atom, and Core i7 CPUs.  Hyper-Threading Technology or HTT is used to improve performance of microprocessors by doing parallel computations or doing multiple tasks at once.  This approach is considered more cost-effective than multiprocessing, which requires replication of microprocessors.

Thermal Design Power

The Thermal Design Power or TDP refers to the maximum amount of power the cooling system in a computer is required to dissipate.  The TDP is typically the maximum power that a CPU would draw when running real applications. This is a guarantee that the computer will be able to handle almost all applications without exceeding the CPU’s thermal limit.

Let us now compare a number of popular Intel and AMD processors according to the specs discussed above.  Take note that indicated prices are average in the market and as of March of 2009.

Future Trends

The CPU battle now is in the multi-core arena.  AMD is planning to ramp up production of its 32-nm processor by middle of next year.  On the other hand, Intel announced that it will be the first in the 32-nm market when it ships the Westmere chips late this year.  But take note that 45-nm chips from both AMD and Intel are still new and very strong in the market.  Intel’s Core i7 and AMD's Phenom II processors are very popular in desktops. For servers, AMD has the 45-nm Opterons and Intel has its Xeon family. These chips are far from obsolete and will still be around for some time before the 32-nm chips take over.  The battle is not only with the chip physical size but with processing power with the introduction of  not only more powerful quad-core processors, but also six and eight cores in the coming years.