The motherboard is the essential main hardware in every computer system. Every piece of hardware plugs directly into this board. Form Factors AT LPX NLX Invented by IBM in the early 1980 s Now obsolete Few variations of size from big to very big Original AT Board was 12 by 12 Only port was for a keyboard First slimline form factor Stands for low profile extended ^ This is slightly controversial Replaced the LPX form factor Doesn t stand for anything just a real cool name. Note: Both the LPX and the NLX provided a central riser slot for a riser card. This was called a Daughterboard. This allowed expansion cards to fit into the Daughterboard horizontally. N.B: An apple a day keeps the doctor away. ATX Invented in 1995 No AT keyboard port, it was replaced with a mini-din (PS/2) port. Position of the PSU was at a better angle. CPU + RAM positioned for easier access RAM closer to the CPU + Northbridge Average size was 12 x 9.6 Micro ATX (µatx) 30% smaller than ATX Uses the same connections Average size was 9.6 x 9.6 1
Flex ATX Motherboards Smallest ATX variant Average size is 9 x 7.5 Also used the same connections ITX Available in 2001 Is a SFF board (Small form factor) 6.7 x 6.7 Nano and Pico ITX Nano (4.7 x 4.7 ) Pico (3.8 x 2.8 ) Used for special routers / embedded devices Proprietary Form Factors Main culprits (Dell / Sony) Boards are meant for certain cases only Laptops have no form factor they are all proprietary Drives us techie s nuts when we need replacements. 2
Expansion Slots and the Expansion Bus Motherboards Expansion Bus Expansion slots are connected to either the North or South Bridge. Sometimes some slots are connected to the North Bridge and others to the South Bridge Plug in a HDD controller card and you will be able to use it as normal, only difference may be speed of use, E.G maybe slower using an expansion slot than using on board controllers. Expansion slots use a different crystal for the speed of the bus. Types of Expansion Slots PCI AGP PCI-X Peripheral Component Interconnect (Intel) Introduced in the early 1990 s Lack of price tag made manufacture s quickly adopt this slot Originally ran at 33 MHz and was 32 bit Can co-exsist with other expansion buses Self configuring and featured PnP There was a 64 bit version of PCI but it is very rare Accelerated Graphics Port Guess what it s used for ;) PCI Extended is a 64 bit wide bus Will accept regular PCI cards More enhanced speeds (PCI-X 66, PCI-x 133, PCI-X 266 + PCI-x 533) Mini-PCI Version of PCI for laptops Mainly used for Wi-Fi and Bluetooth internal cards PCIe (PCI Express) Fastest version of PCI Uses new method (Point to Point) Serial communication PCI uses share parrell communication Has multiple speeds and revisions 3
Expansion Buses Comparison Bus Bus Type Data Path (Bits) Address Lines Bus Frequency Throughput System bus Local 64 32 or 64 Up to 1600 Mhz Up to 3.2 GB/sec PCIe V2 Local Video to 32 lanes Up to 32 lanes 2.5 GHz Up to 500 PCIe V1.1 PCIe V1 Local Video Local Video to 16 lanes to 16 lanes Up to 16 lanes 1.25 GHz Up to 250 Up to 16 lanes 1.25 GHz Up to 250 PCI-X Local I/O 64 32 66, 133, 266 or 533MHz Up to 8.5 GB/sec PCI Local I/O 32 or 64 32 or 64 33, 66 MHz 133, 266 or 532 MB/sec AGP 1x, 2x, 3x, 4x, 8x Local Video 32 NA 66, 75, 100 MHz 266 MB/sec to 2.1 GB/sec FireWire 400 and 800 Local I/O or Expansion 1 Serial NA Up to 800 MB/sec USB 1.1, 2.0 and 3.0 Expansion 1 Serial 3 MHz 12 or 480 Mbs or 5.0 Gbps Motherboard Chips(Chips, hmmm I m hungry)et, The Address Bus and the External Databus North Bridge Deals with high speed interfaces such as RAM / Graphics Card South Bridge Controls lower speed hardware such as USB ports and peripheral ports. 4
Modern CPU s now contain the North Bridge instead of it on being on the motherboard nowadays the motherboard is refered to differently also: Intel (ICH) Input/Output Controller Hub AMD (FCH) Fusion Controller Hub The chipset extends the data bus to every device on the PC and the cpu uses the data bus to move data to and from all the devices on the CPU. Data constantly flows on the external databus between / among the CPU, Chipset, RAM and other devices. Address Bus For the CPU to tell the chipset to send / store data in the memory and it also tells the chipset which section of memory to access and use. External Databus The chipset extends the address bus to all of the devices this way the cpu can use the address bus to send commands to devices just as it communicates with the chipset. 5