Section 1.4: Characteristics of CPUs

A CPU (Central Processing Unit) or the processor is the main component of a computer that does all the processing. For example it processes all the logic statements put to it in the form of programmed software instructions of applications and utilities. The CPU does three main tasks: it uses ALU (Arithmetic Logic Unit) to perform mathematical operations, moves data from one memory location to another, and makes decisions and based on a set of instructions. The performance of a CPU is measured in hertz by its clock rate. It is also used to reference the speed of the CPU.

The two main provides of processors are Intel and AMD. Initially there used to be only single-core processors containing one processing unit were available but now for past few years, dual-core processors that contain two identical processing units and quad-core processors that contain four identical processing units have become available from AMD and Intel.

Section 1.4.1: Intel

Intel brought its first successful CPU 8086 in market in 1970. The other early CPUs include 80286, 80386, and 80486. Then the Pentium processors were introduced in 1993. These were more advanced. They used 3.1 million transistors, 64 bit data path, 32 bit address and 16 KB on-chip cache. Pentium refers to three generations of CPUs. The first generation Pentiums were 273 pin PGA that ran at 60 MHz or 66 MHz of speed. Second generation were 296 - pin models that ran at speed 75 MHz and 200 MHz. Third generation (MMX) Pentiums had added multimedia extensions which were used to run heavy graphic games.

Pentium Pro released in 1995 were the second and third generation Pentiums. They included quad pipelining, had PGA style, 378 pins and uses socket 8. Pentium II was the next released generation in 1997. It had chips that ranged from 233 MHZ to 400 MHZ. It used SECC instead of PGA to attach to the motherboard. They were designed for singleProcessor only applications. Celeron was a less costly almost half the price alternative for Intel processors. Pentium III was released in 1995 and used two styles: SECC2 connector and PGA- style chip with 370 pins. Pentium IV was released in 2002 and had a speed between 400 MHz to 800 MHz. It used hyperthreading technology. Then the dual core and quad processors came into existence.

Intel processors are difficult to upgrade because it never provides new socket types that are backwards-compatible. A change of processor socket would always mean user of the initial socket type having to change the motherboard, processor and even the RAM memory.

Section 1.4.2: AMD

AMD provides processors such as K6, Athlon, and Duron. AMD's competitor to Pentium II was its K6 processor, which ran between 166 MHz and 300 MHz. Then the processors such as K6-2, having speeds 266 MHz to 475 MHz, and K6-3 having speed 400 MHz to 450MHz were released. AMDs competitor to Pentium III is its Athlon. The AMD processors are backwards-compatible with its predecessor and are therefore easy to upgrade. For example AM3 processors are backwards-compatible with its predecessor,

Socket AM2+. However, a Socket AM2+ processor (cannot run on a Socket AM3 motherboard)

Section 1.4.3: Multi Core Processors

When two or more processors are attached on an integrated circuit to achieve efficiency of all the processors simultaneously then it is called multi core processors. It also provides enhanced performance and reduced power consumption. However, the performance of a multi-core processor strongly depends on the software algorithms and implementation. Multi core processors can be of following types:

  • Dual Core: In dual core set-up, two separate processors are installed in the same computer and into the same socket to get faster connection speed. A dual core processor is nearly twice as powerful as a single core processor with a performance gain of fifty percent. Both Intel and AMD have their Dual core processors in the market.
  • Triple Core: In triple core set-up, three separate processors are installed in the same computer and into the same socket. Triple core processor is introduced by AMD only. It is less expensive as compared to quad core.
  • Quad core: In quad core set-up, four cores or four processors are installed in the same computer and into the same socket. With four processing cores, the processors deliver amazing performance and power efficiency. Combining equivalent CPUs on a single die significantly improves the performance of cache snoop. Both Intel and AMD have their Dual quad processors in the market.

Section 1.4.4: Hyperthreading

Hyper-threading is a technique introduced by Intel and is Intel's trademark technology that improves the parallelization of computations. It enables a single CPU to act like multiple CPU's. It allows allowing multiple threads to run simultaneously with improved reaction and response time. It also provides support for multi-threaded code. In hyperthreading the operating system addresses two virtual processors and shares the workload between each processor core that is physically present whenever possible.

Section 1.4.5: Onchip cache

A cache is a smaller faster memory to copy most frequently used data in the main memory for faster access time. When the processor needs to read or write to a location in main memory, it first checks the data cache, which is much faster than reading from or writing to main memory. There are two types of cache: on-chip with the processor, also known as the "Level-1" cache (L1) or primary cache and off-chip cache also known as the "Level 2" cache (L2) or secondary cache. The multilevel on-chip use high-performance small cache architectures that improve system performance. The L2 cache complements L1 cache by writing back the cache