A+ Certification/Exam Objectives/Hardware/Basics/CPU

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The CPU (Central Processing Unit) is the 'brain' of the computer.

It's typically a square ceramic package plugged into the motherboard, with a large heat sink on top (and often a fan on top of that).

All instructions the computer will process are processed by the CPU. There are many "CPU architectures", each of which has its own characteristics and tradeoffs. The dominant CPU architectures used in personal computing are x86 and PowerPC. x86 is easily the most popular processor for this class of machine (the dominant manufacturers of x86 CPUs are Intel and AMD).

Introduction[edit | edit source]

Most CPUs divide the tasks of interpreting and carrying out the instructions between:

  1. A control unit that directs program flow and
  2. One or more execution units that perform operations on data.

Almost always, a CPU includes a collection of registers to hold operands and intermediate results.

When every part of a CPU sits on a single physical integrated circuit, one calls it a microprocessor. Practically all CPUs manufactured today classify as microprocessors.

The term "CPU" often refers—imprecisely—to other centrally important parts of a computer, such as caches and I/O controllers, especially when those functions exist on the same microprocessor chip as the CPU. With the arrival of multi-core chips, the term CPU can either mean the physical chip (see the picture) mounted on the motherboard, or it can mean the core within the chip.

Manufacturers of desktop computers occasionally erroneously describe the entire personal computer (the system unit or sometimes white box, including the computer case and the computer hardware it contains) as the CPU. Rather, the CPU, as a functional unit, consists of that part of the computer which actually executes the instructions (add, subtract, shift, fetch, etc.).

CPUs contain a small amount of static RAM (SRAM) called a cache. Some processors have two or three levels of cache, containing as much as several megabytes of memory.

Types of CPUs[edit | edit source]

There are many types of CPU's.Many processor architectures can also be characterized by their CPU design, like register size. Today most desktop computers and laser printers have 32-bit processors. Some 64-bit processors are rapidly becoming more widespread. Smaller devices like mobile phones, PDAs, or portable video game devices may have 16 or 8 bit processors. Embedded systems such as microwave ovens, calculators, computer keyboards, and infrared remote controls typically have 8 bit or 4 bit processors.

Intel CPUs[edit | edit source]

Intel is currently the most popular CPU choice in personal computing.

Intel has 10+ types of CPU from which a person may choose.

Classic Pentium CPU Package = MHz/GHz= 60 to 200 MHz Slots/Sockets =

Celeron - SEP, PPGA, FC-PGA, FC-PGA2 Pentium 4 – OOIA/OLGA and FC-PGA2 Itanium – PAC (uses PAC418) Itanium 2 – PAC (uses PAC611)

Sockets 1-7 and Super Socket 7[edit | edit source]

These are the Pentium OverDrive Processor Sockets for Pentium Processor-based Systems.

Socket 4[edit | edit source]

When you look at socket 4 you may be wondering what it's used for. This socket is used for putting a CPU in. Just like all sockets a CPU is put into it to help the computer process information. This socket needed a voltage of 5 volts. This socket was a 273 pin system, meaning that it needed 273 pins put into it from a CPU chip. The CPU chips that were put into this socket had 273 pins. Socket 4 is old school, meaning this is a very, very old socket that was used during the days of the Classic Pentium 60/66.

Classic Pentium CPUs could go from 60 to 200 MHz. These chips are in the 125+ MHz range. Just look at them closer and you'll be able to tell.

Socket 5[edit | edit source]

Socket 5

Intel Socket 5 Specification

Designation: Socket 5

Number of Pins: 320

Pin Rows: 5 (staggered)

Voltage: 3.3 volts

Motherboard Class: Pentium

Supported Processors: Pentium 75-133 MHz, Pentium OverDrive

Description: Socket 5 is the first socket designed for the mainstream (second generation) Pentium processors. It supports low-speed Pentiums from 75 to 133 MHz. Higher-speed Pentiums such as the 166 MHz and 200 MHz, and the newer Pentiums with MMX, will not work in a Socket 5 because they have an extra pin. They must be used in a Socket 7. Pentium OverDrives to upgrade Socket 5 Pentiums exist to allow upgrades to these motherboards. Socket 5 is now obsolete, replaced by Socket 7.

Socket 6[edit | edit source]

Intel Socket 6 Specification

Designation: Socket 6

Number of Pins: 235

Pin Rows: 4

Voltage: 3.3 volts

Motherboard Class: 486

Supported Processors: 486DX4, Pentium OverDrive

Description: Socket 6 is the last 486 class socket standard created by Intel. It is a slightly modified Socket 3, and it never caught on in the marketplace. Presumably, with Intel discontinuing the 486 line of processors, motherboard manufacturers did not see any need to incur the cost of changing their designs from the Socket 3 standard. Socket 6 is not used in modern motherboards.

Socket 7[edit | edit source]

Socket 7 is a 321-pin Zero Insertion Force processor socket and is a superset of the previous 320-pin Socket 5. (1)

The ZIF socket was designed so that the average computer user could upgrade the CPU. It supported Pentium and Pentium MMX processors up to 233 MHz.

SECC[edit | edit source]

(SECC) Single Edge Contact Cartridge. The card has a single edge which is put into a slot. This slot could be Slot 1, Slot 2, and even Slot A.

Each card that goes into a slot is different. SECC card are covered with a plastic black housing. They have a fan and a heatsink that is attached to its housing.

The difference between a SECC card and a SECC-2 (Single Edge Contact Cartridge 2) card is that the SECC-2 card does not use a fan or a heatsink. This is why when you have a SECC-2 card in your computer, you should put in a fan to help it recover from the heat it will generate. The reason the SECC-2 card is called SECC-2 is because it is the second version of SECC.

The SECC-2 card uses Slot 1. Slot 1, also known as SC242, is a connector with 242 contacts. This Slot-type connector is used to attach SECCs that have Pentium III processors onboard and attached to them.

Socket 370[edit | edit source]

Sometimes the motherboard doesn't allow for the PPGA Processor to be put directly onto the main board. Thus, a slocket is needed to be put into a slot on the mother board and have the PPGA put into its Socket 370 adaptation section. PPGA Processors from Intel fit onto a slocket that goes into Slot 1. 370 is the number of pins on the PPGA Celerons. The PPGA Celerons have 370 pins, this is why it goes into a "Socket 370". In case you're still stumped, the Socket 370 only allows 370 pins to be inserted into it.

SSA stands for: Slot-to-Socket Adapter

FC-PGA[edit | edit source]

FC-PGA (Flip Chip Pin Grid Array) CPUs can be installed onto the slocket just like a PPGA CPU can however they need a specific slocket of their own. FC-PGA CPUs also have 370 pins.

The side about FC-PGAs is that you can put a cooler onto them.

External Links for PPGA and FC-PGA: http://www.intel.com/design/quality/celeron/ppga/integration.htm

Socket PAC418[edit | edit source]

Is used for Itanium CPU.

Socket 423[edit | edit source]

Is used for Pentium 4 CPU.

Socket 478[edit | edit source]

Is used for Pentium 4 and Celeron CPU.

Socket 603[edit | edit source]

Socket 603 takes PGA CPU.

Socket 775[edit | edit source]

LGA (Land Grid Array) Socket type, not using Pins anymore, Intel Celeron D, Intel Pentium 4, Intel EE, Intel Pentium D, Intel Core 2 Duo/Extreme CPUs

AMD CPUs[edit | edit source]

AMDK61.jpg AMDK61a.jpg

(Note: The above photos are an AMD K6 300MHZ processor similar to the description below however operates at a slightly lower voltage and is prior to the K6-2)

The above is a first version of an earlier processor created by AMD called AMD-K6-2. The speeds that clocked from this processor are 166 to 500 MHz. This Processor has 321 pins and takes from 2.5 V to 3.5 V from the power supply to power itself up. This CPU is comparable to a Pentium II or a Intel Celeron Processor.

The above is a picture of the processor called AMD-K6-III. This CPU would be put into Super Socket 7. The processor compares to a Pentium II with a MHz between 350 and 450. This current processor is a 450 MHz model.

Slot A[edit | edit source]

AMD's Slot A CPU's were the first attempt at K7. The difference between Athlon and Duron are core capabilities (Duron less cache) and at the end of the Slot A range their voltage requirements and FSB (Front Side Bus) speed as well as what image was used to create them (Barton, ...). They ranged from 400 MHz to 1.6 GHz. They were favoured at one point by overclockers because to increase the processing speed all you needed was a pencil(until soft speed options came along) and were always faster than the Intel equivalents. All need fans and a large heatsink (some as many as 4 fans) as they throw out heat. The format was dropped by AMD because when the computer boxes were moved, the weight of the heatsink would shift and on occasion break the motherboard - in favour of Socket A.

Slot A processors are not compatible with Slot 1 or Slot 2 motherboards and vice versa.

Socket 462/A[edit | edit source]

Is used for AMD Athlon, Duron and Sempron CPUs.

Socket 754[edit | edit source]

AMD Sempron/Athlon 64 CPUs - single memory channel

Socket 939[edit | edit source]

AMD Athlon 64 CPUs - Dual channel memory - chip has 2 on-board memory controllers that work in parallel

Socket 940[edit | edit source]

AMD Opteron CPUs - Primarily for servers, has dual channel memory with error correction, hence the extra pin

AM2 AM2+[edit | edit source]

Newest socket from AMD (7-4-06) - Supports DDR2 Memory - Very similar to the Socket 940 AM2+ socket supports AMD Quad Core processor, looks the same visually as AM2

Chipsets[edit | edit source]

The chipset commonly is divided into two devices, the northbridge, and the southbridge. The northbridge is usually the more powerful of the two, and is the closer chip to the physical CPU.

The northbridge, essentially has a few primary functions. Grabbing/Addressing memory from the RAM, and deploying the contents over the data bus for the CPU to read. The northbridge also controls how much ram can be installed into the system. The other functions is allowing the southbridge and its parts, and the AGP slot to communicate with the CPU. In essence the northbridge acts like sort of a receptionist for the cpu, channeling communication from other parts to communicate directly to the CPU. Today, now that the AGP slot is being phased out, and memory controlers are being implemented directly into CPU cores, the northbridge is becoming marginalized if not completely left out of current designs. One example would be the AMD64 in which the memory functions of the northbridge is now in the CPU core, and there is only a southbridge in the chipset.

The southbridge is another chip in the total chipset. Usually the same size as the northbridge, but further away from the CPU (usually near the BIOS), it controls the communication between various peripheral components. A list of what a common southbridge would control would be, IDE controlers, USB ports, PCI slots, and so on. The southbridge also has many other features, but it depends on the features the board has, since most are embedded into the southbridge.

External links[edit | edit source]