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System Introduction 1-27
3.
CD-ROM Reset [pin-U13 of U21(PX3_CDRST#) of PIIX4].
The reset pin is used to assert
the hard reset needed for the CD-ROM during power up. The reset pin is asserted before
CD-ROM power up and is deasserted after CD-ROM power up and before the buffer is
enabled.
•
Floppy
The floppy has two components involved in the process. The floppy drive and the controller
imbedded in the 87338 super I/O chip. The FDC enable/disabled function is controlled by
87338 chip. In power saving mode, there are following condition happened to floppy drive:
1.
External pin tri-state.
Enabled whenever the floppy is turned off. This control signal is same
to CD-ROM buffer enable pin[pin-M3 of U21(PX3_FDDBEN) of PIIX4], please see CD-
ROM portion for details.
2.
PLL disabled.
Disabled whenever the floppy and both serial channels are inactive or
disabled.
3.
FDC power disable.
Disables the active decode of the floppy unit. This control signal is
same to CD-ROM power control[pin-T14 of U21(PX3_CD/FDPON) of PIIX4], please see
CD-ROM portion for details.
•
Video
The video controller has two interfaces for controlling power consumption. The sleep mode is
controlled by software and is performed by BIOS calls. The suspend operation is controlled by
a PX3_VDPD signal (pin-N1 of PIIX4). The video timer is not controlled or retriggered by video
activity. Instead, the timer is retriggered by PS/2 mouse and keyboard activity.
•
Serial port
The serial port is a UART1 and is contained within the 87368 super I/O chip. The UART1
operates off of a 14 MHz clock. The serial port also has a transceiver, a MAX211. Therefore,
there are several steps to the power conservation of the serial port as below:
1. Disable the UART1 decode in the 87338 chip.
2. Tri-state the UART1 output pins.
3. Assert the Power Down pin[pin M4(PX3_SPPD#) of PIIX4] on the MAX3243 chip.
The MAX3243 pin25-PX3-SPPD# of MAX3243 chip will still pass
through the Ring Indicate signal even while in the power down
mode(if the Resume On Modem Ring in BIOS Setup is set to
enabled). .
4. Disable the 14MHz clock (If the floppy and the SIR are also disabled).
If the 14MHz is disabled through the 87336 power down mode, then
all serial and floppy functions will fail.