4 replies
by parvus1202
by cg it
by thechas
There are 3 "general" styles of motherboards.
AT, ATX, and Combo.
AT:
Full size 5 pin DIN keyboard connector
Peripherals may not be on the motherboard. If they are on-board, header connectors are used with ribbon cables that go to the connectors that mount on the case.
Single row 12 pin power connector. 2 6 pin connectors plug into the 12 pin header from the power supply.
Power switch switches the AC main power to the power supply. When the power switch is OFF the computer is fully off.
AT systems started with the 286 CPU.
ATX:
Mini-DIN (PS/2) connectors for keyboard and mouse.
I/O connector block
Double row 20 pin power connector
Power supply is ALWAYS part way on. 5 volt "standby" power is always on the motherboard.
The power switch is a momentary push button that in effect sends a signal to the power control circuit on the motherboard. Telling the motherboard to turn the power on.
Started to show up on "high-end" 486 systems.
Combo boards:
These have the Micro AT form factor including the full size DIN keyboard connector.
Most combo boards have a header for a PS/2 mouse connector. Some also supported PS/2 keyboard connectors.
A "true" combo board has both the AT and ATX power connectors.
Chas
by mfd_patna
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