Store Global/Interrupt Descriptor Table Register (sgdt, sidt)

sgdt    	mem48
sidt    	mem48

Operation

DTR -> mem48

Description

The contents of the descriptor table register is copied by sgdt/sidt to the six bytes of memory specified by the operand. The first word at the effective address is assigned the LIMIT field of the register. If the operand-size attribute is 32-bits:

• The base field of the register is assigned to the next three bytes.

• The fourth byte is written as zero.

• The last byte is undefined.

If the operand-size attribute is 16-bits, the 32-bit BASEfield of the register is assigned to the next four bytes.

sgdt/sldt are not used in application programs, they are used in operating systems.

Example

Copy the contents of the Global Descriptor Table Register to the specified memory location:

sgdt 0x55555555

Copy the contents of the Interrupt Descriptor Table Register to the effective address (addressed by the EBX register plus an offset of 5):

sidt 5 (%ebx)