Computer components are attached to a large circuit board called the motherboard. The motherboard holds the CPU, hard drive, CD-ROM drive, floppy drive, video cards, memory and other card devices. They all fit or attach to the motherboard. On the motherboard itself, the places that the components attach to are called slots and sockets. A standard Pentium motherboard today, would have four ISA slots, four PCI slots, four 72-pin SIMM (main memory/RAM) sockets, and a cache socket. The motherboard is dependent on the type and speed of the central processing unit (CPU). This is important since the circuitry of the motherboard needs to handle the directions of the CPU. Below are the different components that are found on the motherboard.
There are three choices for bus systems for the motherboard.
VL-Bus (VESA Local bus). This bus was originally used with the 486 computers and was limited in the number of slots to add on devices. Used for add-in cards such as video display.
PCI Bus: This bus is considered the standard. It can transfer data 64-bit at a time with rates up to 66 MHz.
COMBO Bus. This bus is a combination of of a PCI bus and VL-Bus. It allows the use of both type of add-in cards. This card is recommended since it meets a variety of needs.
All motherboards come equipped with with slots for older ISA plug-in-cards. This way the older 8-bit and 16-bit ISA and 32-bit EISA can still be used in the newer PCs.
The motherboard contains circuits that allows data to travel electronically along pathways. This data needs some system or way to control the communication ports, fixed drives, floppy drives, parallel port, and other devices. This is managed through the I/O or in/out. You can buy a computer with I/O onboard, which means that it is already on the motherboard. Otherwise you will need to by a separate add-on card which takes up another slot on the motherboard. This add-on may take up valuable space if you want to add more devices to your system.
Characteristics of a good I/O
EIDE (Enhanced IDE) interface able to handle:
4 fixed drives 2 floppy drives
1 parallel port
2 high speed serial communications port (with 16550 UART)
How to speed up main memory? Why by using cache. The standard cache uses four bytes of data transferred to the CPU in eight clock cycles. Two types of Cache Memory: This is determined by the design of the mother board.
RAM chips (Static RAM) also called SRAM is called the standard RAM. It comes in different sizes. SRAM comes in the following configurations: 32K X 8 SRAM ; 64K X 8 SRAM; 128K X 8 SRAM. How much you add is determined by the number of sockets that the motherboard has to hold the SRAM.
COAST module A way to speed cache is to use pipeline burst. In pipeline burst mode, the four bytes of data can be transferred in five clock cycles. This is a feature of Pentium computers. If the cache is not already built in on the motherboard it usually can be added separately. This memory is called COAST (Cache On A STick). They are small circuits that can be added to the motherboard.
The advances in technology have caused the change in the types of memory available. Older motherboards had sockets that accept 30-pin SIMMS(memory). This is older technology. Memory is currently very inexpensive. Most motherboards are being built to accept only 72-pin SIMMS. The bottom of the edge of the SIMM has 72 fingers or connections that line up with the sockets on the motherboard. There are two banks of two sockets each called Bank 0 and Bank 1. Both banks have to contain SIMMS so that they have to be added in pairs. SIMMS can not be added to the motherboard as single SIMMS. You must fill Bank 0 before Bank 1.
What are the Characteristics of RAM?
SIMM Memory- this refers to the amount of RAM that the SIMM adds to the computer. It is measured in MB for megabytes or millions of bytes.
Parity or Non-parity- parity checking is used to check the validity of
data going through the memory. It makes the memory more reliable. Parity
memory has 9 bits of memory rather than eight. One of the bits is used to
check the other memory to make sure it is correct. This memory is important
if you want very valid data. Also make sure that if you buy memory that is
supported by your motherboard.
Data Access Time- measured in nanoseconds (ns) or one-billionth of a second the access time is the time used to retrieve data located within a SIMM. The lower the MB SIMM the slower the speed. An 8 MB SIMM has a slower access time than a 16 MB SIMM. Mixing an 8 MB SIMM with a 16 MB SIMM slows the access time to the slower SIMM. The lower the number of nanoseconds, the faster the machine.
EDO and Non-EDO SIMMS-(Extended Data Out) This simm is the newest model of memory. It works 15 percent faster than Non-EDO memory. It will fit into a motherboard that supports 72-pin SIMMS, but will only produce the faster access time if the motherboard is designed to support it. Be sure and buy memory in pairs. Mixing memory from more than one manufacturer is not considered good practice. These motherboards usually have four sockets to six sockets that accept 72-pin SIMMS. If looking for a computer choose EDO memory, it is faster. Parity is another consideration. If the memory is parity memory, make sure that the motherboard supports parity checking.
The chipset refers to the processing chip used on the motherboard. The board must support the type of chipset that is used on the motherboard. For this reason, when replacing a processing chip, be sure and check with the manufacturer before buying a replacement. The electronic circuits need to be able to support the chip. This is also true if replacing or upgrading a motherboard. The chipset helps to determine what type of bus, cache, power supply, memory, etc. If buying a new motherboard make sure that you get a user's manual, it is needed to configure(setting jumpers and switches) your motherboard.
The BIOS is a small chip on the motherboard that has the program instructions for start-up and testing of the computer when it is turned on. It contains a small amount of memory that is programmed to remember these instructions. The BIOS also is in charge of setting the new "Plug and Play" devices and also for handling the input and output of data. The BIOS is programmable and can be changed and updated. A computer diskette is usually supplied with the motherboard with this purpose in mind. The the most recent BIOS that can be found in computers is called Flash BIOS.
Various built in features of motherboards:
Motherboards can come with features already built in such as built in mouse ports, game ports, video card displays, sound cards, and SCSI I/O Adapters. The problem with this type of motherboard means that when newer features are added to that device, it cannot be upgraded. Plug and Play cards seem to be the thing of the future and allow for the system to be upgraded.
What's the Dipping all About?
When motherboards are set up, they are said to be configured. In the user's manual there are instructions on what the settings should be for the switches. Dip switches are soldered to a plastic base on the top of the motherboard. They are labeled to an on or off position. They can be moved with a ballpoint pen.
And then there is the Jumper!
Another type of switch is a jumper. It consists of three metal pins sticking out of the motherboard. They are labeled also starting with a "J". The on/off of the jumper is controlled by putting a cap on two of the pins.
Connectors are pins located on the motherboard, usually 2 to 40 pins. Connectors are also plugs at the ends of wires or cables which attach to the pins.
For the more advanced user click here to learn how to install motherboards.
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