Specifications

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Intel

Quark Core—System Management Mode (SMM) Architectures

Intel

Quark SoC X1000 Core

Developer’s Manual October 2013

140 Order Number: 329679-001US

If the system executes back-to-back SMI# requests, the second SMM handler must not

set the I/O instruction restart slot (see Section 8.6.6).

8.5.4 SMM Base Relocation

The Intel

Quark SoC X1000 Core provides a control register, SMBASE. The address

space used as SMRAM can be modified by changing the SMBASE register before exiting

an SMI# handler routine. SMBASE can be changed to any 32-Kbyte aligned value

(values that are not 32-Kbyte aligned cause the processor to enter the shutdown state

when executing the RSM instruction). SMBASE is set to the default value of 30000H on

RESET, but is not changed on SRESET. If the SMBASE register is changed during an

SMM handler, all subsequent SMI# requests initiate a state save at the new SMBASE

(see Figure 62).

Figure 62. SMM Base Location

The SMBASE slot in the SMM state save area is used to indicate and change the SMI#

jump vector location and the SMRAM save area. When bit 17 of the SMM revision

identifier is set, then this feature exists and the SMRAM base and jump vector are as

indicated by the SMM base slot. During the execution of the RSM instruction, the

processor reads this slot and initializes the processor to use the new SMBASE during

the next SMI#. During an SMI#, the processor performs a context save to the new

SMRAM area pointed to by the SMBASE, stores the current SMBASE in the SMM Base

slot (offset 7EF8H), and then start execution of the new jump vector based on the

current SMBASE.

The SMBASE must be a 32-Kbyte aligned, 32-bit integer that indicates a base address

for the SMRAM context save area and the SMI# jump vector. For example when the

processor first powers up, the minimum SMRAM area is from 38000H-3FFFFH. The

default SMBASE is 30000H. Hence the starting address of the jump vector is calculated

by:

SMBASE + 8000H

While the starting address for the SMRAM state save area is calculated by:

SMM Base + [8000H + 7FFFH]

Hence, when this feature is enabled, the SMRAM register map is addressed according

to the above formulas (see Figure 63).

Table 46. I/O Instruction Restart Value

Value at Entry Value at Exit Comments

00H 00H Do not restart trapped I/O instruction

00H 0FFH Restart trapped I/O instruction

7EF8H

SMM Base