82845G Datasheet, PDF (37/193 Pages) Intel Corporation – Intel 82845G/82845GL/82845GV Graphics and Memory Controller Hub (GMCH)

Signal Description
Table 2-2 shows the VTT/VDD, VREF, RCOMP, and VSWING levels for the various interfaces.
Table 2-2. Voltage Levels and RCOMP for Various Interfaces
Interface
Core
AGTL+
AGP/DVO
HI1.5
DDR - SSTL_2
SDR - LVTTL
VTT/VDD
(Volts)
1.5 V
1.15 -1.75 V⁽¹⁾
1.5 V
1.5 V
1.25/2.5 V
3.3 V
VREF
(volts)
NA
2/3 * VTT
0.5 * VDD
0.35
0.5 * VDD
0.5 * VDD
RCOMP
(Ω)
NA
25
40
69
60
20
RCOMP
term
Note 2
Vswing
(Volts)
NA
1/3*VTT
NA
0.7
NA
NA
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
Signal Name
VCC
VSS
VCCAGP
VCCA_FSB
VTTFSB
VTTDECAP
VCCA_HI
VCCHL
VCCA_DPLL
VCCA_DAC
VSSA_DAC
VCCGPIO
VCCSM
VCCA_SM
VCCQSM
Description
VCC for 1.5 V core.
GND supply.
VCC for AGP – 1.5 V.
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.
VTT supply for PSB, having a range of 1.15 V–1.75 V.
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.
Analog VCC for the HI/AGP PLL – 1.5 V. Does not require special filtering.
VCC for Hub Interface – 1.5 V.
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.
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.
Analog Vss for the DAC. This supply should go directly to motherboard ground.
Vcc for GPIO – 3.3 V.
Vcc for System Memory – 3.3 V for SDR, 2.5 V for DDR.
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.
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.
Intel^® 82845G/82845GL/82845GV GMCH Datasheet
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