AMD AMD5K86 - FIGURE 6-2. Default SMM Memory Map

AMD~
AMD5K!J6 Processor Technical Reference Manual
1 8524BjO-Marl 996
During boot, the address decoder must allow BIOS to address
the SMM memory area in the main memory address space
without entering into the SMM mode in order to initialize it
with configuration parameters and the SMM service routine.
Thereafter, the ~IOS typically remaps the area from its default
location in low memory to high or extended memory, as shown
in Figure 6·1. After the remapping by BIOS, the address
decoder must allow only the processor to access the SMM memo
ory area. Other bus masters must be prevented from accessing
it, unless the system design specifically calls for such access.
System Design