DR7

EFLAGS

CR0

0

31

Top of SMM

-4h

-8h

-Ch

-10h

-14h

-18h

-1Ch

-20h

-24h

-28h

P

Current IP

Next IP

Reserved

CS Selector

CS Descriptor (Bits 63-32)

CS Descriptor (Bits 31-0)

Reserved

ESI or EDI

I

1713503

31

16 15

0

31

2 1 0

-2Ch

-30h

Address Space

3

S

I/O Write Address

I/O Write Data Size

I/O Write Data

16 15

Figure 3 - 1.

SMM Memory Space Header

ST486DX - SMM SOFTWARE CONSIDERATIONS

25

save other registers and access data in SMM memory. To use any other register the SMM program-

mer must first save the contents using the SVDC instruction for segment registers or MOV opera-

tions for general purpose registers (See SGS Thomson SMM instruction description Section 2.3).

It is possible to save all the CPU registers as needed. See Section 3.3 for an example saving and re-

storing the entire CPU state.