82443BX Datasheet, PDF (116/132 Pages) Intel Corporation – Host Bridge/Controller

Functional Description
SDRAM Power Down Mode
The 82443BX supports SDRAM power down mode. The 82443BX also provides a capability to
dynamically enter the SDRAM into low power mode when DRAM rows are idle and resume
DRAM activity when transactions request the access to DRAM.
SMRAM Functions
The 82443BX provides the normal SMRAM range mapping, in the areas below 1MB, as well as
extended SMRAM ranges that are mapped in cacheable ranges above 1MB. In addition, the
82443BX provides the normal control mechanism to initialize, close for data accesses and lock the
SMRAM range.
Summary of ACPI Functions
The 82443BX provides an optional decoding of pm2_control register in IO port 22h. This IO port
can be used to disable the 82443BX arbiters for PCI and AGP initiated cycles.
Desktop vs. Mobile Power Management Functions
In general, all mobile functions of the 82443BX are available in the desktop configuration. Due to
system design limitations, however, certain functions are not supported in a desktop environment
(i.e., POS/C3 state).
In Mobile systems, when system exits low power modes such as deep sleep or POS, the AGP
devices should not generate a request, using AGP semantics, for a duration of at least 33 usec.
System Power Modes
Table 4-14 provides an overview of how the above features map into system-wide low power
modes.
4-30
82443BX Host Bridge Datasheet