CPU socket
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The Socket 370 processor socket, a ZIF type PGA socketA CPU socket or CPU slot is a connector on a computer's motherboard that accepts a CPU and forms an electrical interface with it. As of 2007, most desktop and server computers, particularly those based on the Intel x86 architecture, include socketed processors.

Most CPU-sockets interfaces are based on the pin grid array (PGA) architecture, in which short, stiff pins on the underside of the processor package mate with holes in the socket. To minimize the risk of bent pins, zero insertion force (ZIF) sockets allow the processor to be inserted without any resistance, then grip the pins firmly to ensure a reliable contact after a lever is flipped.

As of 2007, several current and upcoming socket designs use land grid array (LGA) technology instead. In this design, it is the socket which contains pins. The pins contact pads or lands on the bottom of the processor package.

In the late 1990s, many x86 processors fit into slots, rather than sockets. CPU slots are single-edged connectors similar to expansion slots, into which a PCB holding a processor is inserted. Slotted CPU packages offered two advantages: L2 cache memory could be upgraded by installing an additional chip onto the processor PCB, and processor insertion and removal was often easier. However, slotted packages require longer traces between the CPU and chipset, and therefore became unsuitable as clock speeds passed 500 MHz. Slots were abandoned with the introduction of AMD's Socket A and Intel's Socket 370.

SECOND TRINAL(First Assignment)

Backplane Systems
Backplane systems use a main card with slots to plug all of the PC components into. These systems typically reside in industrial application due to the cost. There are two types of backplane systems, active and passive. The passive system has a main card with slots mounted on the card and no circuitry on the card. Each piece of the PC is mounted on its own card and then plugged into the backplane. An active backplane has some circuitry mounted on the backplane but not a CPU. The card that has the CPU mounted on it is called the processor complex. This setup allows the user to swap or upgrade components very quickly. Unfortunately, there is no standard for the cards that plug into the backplane so you are limited to what the specific manufacturer sells. The backplane systems are all rack mount and the system bus is fixed.
Full-Size AT

NLX.

Boards based on the NLX form factor hit the market in the late 1990's. This "updated LPX" form factor offered support for larger memory modules, tower cases, AGP video support and reduced cable length. In addition, motherboards are easier to remove. The NLX form factor, unlike LPX is an actual standard which means there is more component options for upgrading and repair.

LPX

White ATX is the most well-known and used form factor, there is also a non-standard proprietary form factor which falls under the name of LPX, and Mini-LPX. The LPX form factor is found in low-profile cases (desktop model as opposed to a tower or mini-tower) with a riser card arrangement for expansion cards where expansion boards run parallel to the motherboard. While this allows for smaller cases it also limits the number of expansion slots available. Most LPX motherboards have sound and video integrated onto the motherboard. While this can make for a low-cost and space saving product they are generally difficult to repair due to a lack of space and overall non-standardization. The LPX form factor is not suited to upgrading and offer poor cooling.

ATX

With the need for a more integrated form factor which defined standard locations for the keyboard, mouse, I/O, and video connectors, in the mid 1990's the ATX form factor was introduced. The ATX form factor brought about many chances in the computer. Since the expansion slots were put onto separate riser cards that plugged into the motherboard, the overall size of the computer and its case was reduced. The ATX form factor specified changes to the motherboard, along with the case and power supply. Some of the design specification improvements of the ATX form factor included a single 20-pin connector for the power supply, a power supply to blow air into the case instead of out for better air flow, less overlap between the motherboard and drive bays, and integrated I/O Port connectors soldered directly onto the motherboard. The ATX form factor was an overall better design for upgrading.
micro-ATXMicroATX followed the ATX form factor and offered the same benefits but improved the overall system design costs through a reduction in the physical size of the motherboard. This was done by reducing the number of I/O slots supported on the board. The microATX form factor also provided more I/O space at the rear and reduced emissions from using integrated I/O connectors.

AT
AT & Baby ATPrior to 1997, IBM computers used large motherboards. After that, however, the size of the motherboard was reduced and boards using the AT (Advanced Technology) form factor was released. The AT form factor is found in older computers (386 class or earlier). Some of the problems with this form factor mainly arose from the physical size of the board, which is 12" wide, often causing the board to overlap with space required for the drive bays.
Following the AT form factor, the Baby AT form factor was introduced. With the Baby AT form factor the width of the motherboard was decreased from 12" to 8.5", limiting problems associated with overlapping on the drive bays' turf. Baby AT became popular and was designed for peripheral devices — such as the keyboard, mouse, and video — to be contained on circuit boards that were connected by way of expansion slots on the motherboard.
Baby AT was not without problems however. Computer memory itself advanced, and the Baby AT form factor had memory sockets at the front of the motherboard. As processors became larger, the Baby AT form factor did not allow for space to use a combination of processor, heatsink, and fan. The ATX form factor was then designed to overcome these issues.
Key Terms To Understanding Motherboard Form Factors
motherboardThe main circuit board of a microcomputer.
form factorThe physical size and shape of a device. It is often used to describe the size of circuit boards.
ATShort for advanced technology, the AT is an IBM PC model introduced in 1984.
ATX