Datasheet

Intel
®
82845G/82845GL/82845GV GMCH Datasheet 37
Signal Description
Table 2-2 shows the VTT/VDD, VREF, RCOMP, and VSWING levels for the various interfaces.
NOTE:
1. For the Pentium 4 processor with 512-KB L2 cache on 0.13 Micron Process, VTT range is 1.29 V–1.525 V.
For the Pentium 4 processor with 256-KB L2 cache, VTT range is 1.535 V– 1.75 V
2. Refer to the Intel
®
Pentium
®
4 Processor in 478-Pin Package and Intel
®
845G/845GL/845GV Chipset
Platform Design Guide for details.
2.9 Power and Ground Signals
Table 2-2. Voltage Levels and RCOMP for Various Interfaces
Interface
VTT/VDD
(Volts)
VREF
(volts)
RCOMP
(Ω)
RCOMP
term
Vswing
(Volts)
Core 1.5 V NA NA
Note 2
NA
AGTL+ 1.15 -1.75 V
(1)
2/3 * VTT 25 1/3*VTT
AGP/DVO 1.5 V 0.5 * VDD 40 NA
HI1.5 1.5 V 0.35 69 0.7
DDR - SSTL_2 1.25/2.5 V 0.5 * VDD 60 NA
SDR - LVTTL 3.3 V 0.5 * VDD 20 NA
Signal Name Description
VCC VCC for 1.5 V core.
VSS GND supply.
VCCAGP VCC for AGP – 1.5 V.
VCCA_FSB
Analog Vcc for the Host PLL – 1.5 V. This supply requires special filtering. Refer to the Intel
®
Pentium
®
4 Processor in 478-Pin Package and Intel
®
845G/845GL/845GV Chipset Platform
Design Guide for details.
VTTFSB VTT supply for PSB, having a range of 1.15 V–1.75 V.
VTTDECAP
VTT edge cap connection supply. Do not connect to MB VTT supply. Refer to the Intel
®
Pentium
®
4 Processor in 478-Pin Package and Intel
®
845G/845GL/845GV Chipset Platform
Design Guide for implementation.
VCCA_HI Analog VCC for the HI/AGP PLL – 1.5 V. Does not require special filtering.
VCCHL VCC for Hub Interface – 1.5 V.
VCCA_DPLL
Analog Vcc for the Display PLL – 1.5 V. This supply requires special filtering. Refer to the
Intel
®
Pentium
®
4 Processor in 478-Pin Package and Intel
®
845G/845GL/845GV Chipset
Platform Design Guide for details.
VCCA_DAC
Analog Vcc for the DAC – 1.5 V. Refer to the Intel
®
Pentium
®
4 Processor in 478-Pin
Package and Intel
®
845G/845GL/845GV Chipset Platform Design Guide for supply
requirements.
VSSA_DAC Analog Vss for the DAC. This supply should go directly to motherboard ground.
VCCGPIO Vcc for GPIO – 3.3 V.
VCCSM Vcc for System Memory – 3.3 V for SDR, 2.5 V for DDR.
VCCA_SM
Analog VCC for System Memory DLL – 1.5 V supply requires special filtering. Refer to the
Intel
®
Pentium
®
4 Processor in 478-Pin Package and Intel
®
845G/845GL/845GV Chipset
Platform Design Guide for details.
VCCQSM
Quiet VCC for System Memory – 3.3 V for SDR, 2.5 V for DDR. Supply requires special
filtering. Refer to the Intel
®
Pentium
®
4 Processor in 478-Pin Package and Intel
®
845G/
845GL/845GV Chipset Platform Design Guide for details.