System management mode for Intel processors

[ali hagigat]

I wonder if anybody can explain the system management mode RAM
addresses for Intel Pentium III/815/ICH2.
I know that SMBASE is 30000 after reset. But 815 can define  TSEG (and
HSEG ) and also AB segments some where else. Like TSEG can be 512k or
1M from the top of memory.
Considering  that SMBASE can not be any thing but 30000 as the Intel
manual is saying , from what addresses CPU instructions are fetched
after SMI# interrupt at last?

[Rudolf Marek]

Hi,

Thanks for meaningful query. The 30000h is just a value after reset. The BIOS 
will invoke SMI, the code will get executed from SMIBASE+8000 (so 38000) and SMI 
code will change the save state area and relocate the SMM handler elsewhere to 
TSEG or ASEG (hidden bellow video memory A0000).

Thanks
Rudolf