Functional Description
SDRAM Suspend Refresh
When the 82443BX is configured for 3 DIMMs, six CKE signals are provided. When the 82443BX
is configured for 4 DIMMs, a single GCKE (global CKE) is provided to allow an external device to
correctly drive the external CKE signals to the SDRAM devices. An additional 3 DIMM
configuration is where only CKE0 is provided. A detailed description of the DRAM signal
functions is given in the Chapter 2, “Signal Description”.
For the Registered DIMMs the CKE function is not supported. The stacking technology used for
registered DIMMs prohibits the use of the CKE function. For registered DIMMs, components are
stacked on top of one another. The stacked components are physically in the same row, but
logically in separate rows. The stacked components connect all pins together, except for the CS#
pin, in order to address components in different rows. Since the CKE pins for the components are
connected together, and the components are logically in different rows, the CKE function is not
supported.
Table 4-18. SDRAM Suspend Refresh Configuration Modes
MM
CONFIG
SDRAM
PWR
FUNCTION
3 DIMM, CKE[5:0] driven, self-refresh entry staggered. SDRAM dynamic
power down available.
0
1
0
0
X
1
3 DIMM, CKE0 only, self-refresh entry not staggered. SDRAM dynamic power
down unavailable.
4 DIMM, GCKE only, self-refresh entry staggered. SDRAM dynamic power
down unavailable.
EDO DRAM Suspend Refresh
The 82443BX NB supports two modes of EDO refresh during suspend: CAS-before-RAS and Self-
refresh. The refresh mode is dependent on the Suspend Refresh type bit (SRT) in the Miscellaneous
Control Register.
4.8.4
Clock Control Functions
The 82443BX implements an independent Clock Gating power savings feature to reduce its own
average power consumption. The 82443BX clock gating functions works along with the primary
PCI bus CLKRUN# function.
The Clock Gating function is enabled by setting the GCLKEN Configuration bit. This function
default value is 0. The AGP interface’s clock domain can be permanently disabled by the AGP_DIS
configuration bit. This allows further power savings in systems that AGP is not used.
CLKRUN Clocking States
There are three states in the CLKRUN# protocol:
•
•
Clock Running: The clock is running and the bus is operational.
Clock Stop Request: The central resource has indicated on the CLKRUN# line that
the clock is about to stop.
•
Clock Stopped: The clock is stopped with CLKRUN# being monitored for a restart.
82443BX Host Bridge Datasheet
4-35
ETC [ ETC ]
