DTR -> mem48
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.
Copy the contents of the Global Descriptor Table Register to the specified memory location:
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)