Upgrading and Repairing PCs

Motherboard Interface Connectors

There are a variety of connectors on a modern motherboard. Figure 4.49 shows the locations of these connectors on a typical motherboard (using the Intel D845PEBT2 model as the example). Several of these connectors, such as power supply connectors, serial and parallel ports, and keyboard/mouse connectors, are covered in other chapters. Tables 4.45–4.55 contain the pinouts of most of the other different interface and I/O connectors you will find.

Table 4.45. Infrared Data (IrDA) Pin-Header Connector

Pin	Signal	Pin	Signal
1	+5V	4	Ground
2	Key	5	IrTX
3	IrRX	6	CONIR (Consumer IR)

Table 4.46. Battery Connector

Pin	Signal	Pin	Signal
1	Gnd	3	KEY
2	Unused	4	+6V

Table 4.47. LED and Keylock Connector

Pin	Signal	Pin	Signal
1	LED Power (+5V)	4	Keyboard Inhibit
2	KEY	5	Gnd
3	Gnd

Table 4.48. Speaker Connector

Pin	Signal	Pin	Signal
1	Ground	3	Board-Mounted Speaker
2	KEY	4	Speaker Output

Table 4.49. Microprocessor Fan Power Connector

Pin	Signal Name
1	Ground
2	+12V
3	Sense tachometer

Table 4.50. Chassis Intrusion (Security) Pin-Header

Pin	Signal Name
1	Ground
2	CHS_SEC

Table 4.51. Wake on LAN Pin-Header

Pin	Signal Name
1	+5 VSB
2	Ground
3	WOL

Table 4.52. Wake on Ring Pin-Header

Pin	Signal Name
1	Ground
2	RINGA

Note Some boards have a board-mounted piezo speaker. It is enabled by placing a jumper over pins 3 and 4, which routes the speaker output to the board-mounted speaker. Removing the jumper enables a conventional speaker to be plugged in.

Caution Do not place a jumper on this connector; serious board damage will result if the 12V is shorted to ground.

Table 4.53. CD Audio Connector

Pin	Signal Name	Pin	Signal Name
1	CD_IN-Left	3	Ground
2	Ground	4	CD_IN-Right

Table 4.54. Telephony Connector

Pin	Signal Name	Pin	Signal Name
1	Audio Out (monaural)	3	Ground
2	Ground	4	Audio In (monaural)

Table 4.55. ATAPI-Style Line In Connector

Pin	Signal Name	Pin	Signal Name
1	Left Line In	3	Ground
2	Ground	4	Right Line In (monaural)

Some of Intel's motherboards, as well as those made by other motherboard manufacturers, use a single row of connectors for the front panel, as shown in Figure 4.50.

Table 4.56 shows the designations for the front-panel motherboard connectors used on some Intel ATX motherboards.

Table 4.56. ATX Motherboard Front Panel Connectors

Connector	Pin	Signal Name
Speaker	27	SPKR_HDR
	26	PIEZO_IN
	25	Key
	24	Ground
Reset	23	SW_RST
	22	Ground
none	21	No connect/Key
Sleep/Power LED	20	PWR_LED
	19	Key
	18	Ground
none	17	No connect/Key
Hard Drive LED	16	HD_PWR
	15	HD Active#
	14	Key
	13	HD_PWR +5V
none	12	No connect
IrDA	11	CONIR (Consumer IR)
	10	IrTX
	9	Ground
	8	IrRX
	7	Key
	6	+5V
none	5	No connect
Sleep/Resume	4	SLEEP_PU (pullup)
	3	SLEEP
Power On	2	Ground
	1	SW_ON#