User Guide

8081
8081
N/B Maintenance
N/B Maintenance
83
5.2 Intel 82855GM Graphics and Memory Controller Hub (GMCH)
Voltage Reference, PLL Power Signals
Signal Name Type Description
Host Processor
HXRCOMP
Analog Host RCOMP: Used to calibrate the Host AGTL+ I/O buffers.
HYRCOMP
Analog Host RCOMP: Used to calibrate the Host AGTL+ I/O buffers.
HXSWING
Analog Host Voltage Swing (RCOMP reference voltage): These signals
provide a reference voltage used by the PSB RCOMP circuit.
HYSWING
Analog Host Voltage Swing (RCOMP reference voltage): These signals
provide a reference voltage used by the PSB RCOMP circuit.
HDVREF[2:0]
Ref
Analog
Host Data (input buffer) VREF: Reference voltage input for the
data signals of the Host AGTL+ Interface. Input buffer differential
amplifier to determine a high versus low input voltage.
HAVREF
Ref
Analog
Host Address (input buffer) VREF: Reference voltage input for
the address signals of the Host AGTL+ Interface. This signal is
connected to the input buffer differential amplifier to determine a
high versus low input voltage.
HCCVREF
Ref
Analog
Host Common Clock (Command input buffer) VREF: Reference
voltage input for the common clock signals of the Host AGTL+
Interface. This signal is connected to the input buffer differential
amplifier to determine a high versus low input voltage.
VTTLF
Power PSB Power Supply: VTTLF is the low frequency connection from
the board. This signal is the primary connection of power for
GMCH.
VTTHF
Power PSB Power Supply: VTTHF is the high frequency supply. It is for
direct connection from an internal package plane to a capacitor
placed immediately adjacent to the GMCH.
NOTE: Not to be connected to power rail.
System Memory
SMRCOMP
Analog System Memory RCOMP: This signal is used to calibrate the
memory I/O buffers.
SMVREF_0
Ref
Analog
Memory Reference Voltage(Input buffer VREF):Reference
voltage input for Memory Interface.
Input buffer differential amplifier to determine a high versus low
input voltage.
SMVSWINGH
Ref
Analog
RCOMP reference voltage: This is connected to the RCOMP
buffer differential amplifier and is used to calibrate the I/O buffers.
SMVSWINGL
Ref
Analog
RCOMP reference voltage: This is connected to the RCOMP
buffer differential amplifier and is used to calibrate the I/O buffers.
VCCSM
Power Power supply for Memory I/O.
VCCQSM
Power Power supply for System Memory clock buffers.
VCCASM
Power Power supply for System Memory logic running at the core voltage
(isolated supply, not connected to the core).
Voltage Reference, PLL Power Signals (Continued)
Signal Name Type Description
Hub Interface
HLRCOMP
Analog Hub Interface RCOMP: This signal is connected to a reference
resistor in order to calibrate the buffers.
PSWING
Ref
Analog
Input buffer VREF: Input buffer differential amplifier to determine
a high versus low input voltage.
VCCHL
Power Power supply for Hub Interface buffers
DVO
DVORCOMP
Analog Compensation for DVO: This signal is used to calibrate the DVO
I/O buffers.
GVREF
Ref
Analog
Input buffer VREF: Input buffer differential amplifier to determine
a high versus low input voltage.
VCCDVO
Power Power supply for DVO.
GPIO
VCCGPIO
Power Power supply for GPIO buffers
DAC
REFSET
Ref
Analog
Resistor Set: Set point resistor for the internal color palette DAC.
VCCADAC
Power Power supply for the DAC
VSSADAC
Power Ground supply for the DAC
LVDS
LIBG
Analog LVDS reference current: signal connected to reference resistor.
VCCDLVDS
Power Digital power supply.
VCCTXLVDS
Power Data/Clk Tx power supply.
VCCALVDS
Power Analog power supply.
VSSALVDS
Power Ground supply for LVDS.
Clocks
VCCAHPLL
Power Power supply for the Host PLL.
VCCAGPLL
Power Power supply for the Hub/DVO PLL.
VCCADPLLA
Power Power supply for the display PLL A.
VCCADPLLB
Power Power supply for the display PLL B.
Core
VCC
Power Power supply for the core.
VSS
Power Ground supply for the chip.