82815 GMCH
R
Datasheet
29
2.4.
Display Cache Interface Signals
Some of the Display Cache interface signals are multiplexed with AGP interface signals. Display Cache
interface signals only function as documented in this section when the GMCH integrated graphics is
enabled (GMCH AGP interface disabled). Refer to Section 2.11 for multiplexing map of AGP to Display
Cache interface signals.
Signal Name
Type
Description
LCS#
O
CMOS
Chip Select.
For the memory row configured with SDRAM, this pin performs the
function of selecting the particular SDRAM components during the active state.
LDQM[3:0]
O
AGP
Input/Output Data Mask.
These pins control the memory array and act as
synchronized output enables during read cycles and as a byte enables during write
cycles.
LRAS#
O
CMOS
SDRAM Row Address Strobe.
The LRAS# signal is used to generate SDRAM
Command encoded on LRAS#/LCAS#/LWE# signals. When LRAS# is sampled
active at the rising edge of the SDRAM clock, the row address is latched into the
SDRAMs.
LCAS#
O
CMOS
SDRAM Column Address Strobe.
The LSCAS# signal is used to generate
SDRAM Command encoded on LSRAS#/LSCAS#/LWE# signals. When LSCAS# is
sampled active at the rising edge of the SDRAM clock, the column address is
latched into the SDRAMs.
LMA[11:0]
O
AGP
Memory Address.
LMA[11:0] are used to provide the multiplexed row and column
address to SDRAM.
LWE#
O
CMOS
Write Enable Signal.
LWE# is asserted during writes to SDRAM.
LMD[31:0]
I/O
AGP
Memory Data.
These signals are used to interface to the SDRAM data bus of
SDRAM array.
L_FSEL
I
CMOS
Display Cache Frequency Select.
This signal indicates whether the display cache
operates at 100 MHz or 133 MHz. The value of this pin is sampled at deassertion of
CPURST# to determine display cache frequency.
HIGH = 133 MHz (Default)
LOW = 100 MHz
Note: L_FSEL has a weak internal pull-up enabled during reset.
Note: 100 MHz display cache is a non-validated feature and should be
implemented only if OEM performs validation specifically on this feature.