
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
(
)
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.
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.
VCCA_FSB
VTTFSB
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.
VTTDECAP
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.
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.
VCCA_DAC
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.