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Intel Pentium CPU Instruction Set Reference

SLDT instruction - Store Local Descriptor Table Register

Code Mnemonic Description
0F 00 /0 SLDT r/m16 Stores segment selector from LDTR in r/m16
0F 00 /0 SLDT r/m32 Store segment selector from LDTR in low-order 16 bits of r/m32


Stores the segment selector from the local descriptor table register (LDTR) in the destination operand. The destination operand can be a general-purpose register or a memory location. The segment selector stored with this instruction points to the segment descriptor (located in the GDT) for the current LDT. This instruction can only be executed in protected mode.

When the destination operand is a 32-bit register, the 16-bit segment selector is copied into the lower-order 16 bits of the register. The high-order 16 bits of the register are cleared to 0s for the Pentium Pro processor and are undefined for Pentium, Intel486, and Intel386 processors. When the destination operand is a memory location, the segment selector is written to memory as a 16-bit quantity, regardless of the operand size.

The SLDT instruction is only useful in operating-system software; however, it can be used in application programs.

Operands Bytes Clocks
r16 3 2 NP
mem16 3 + d(0 - 2) 2 NP


ID unaffected DF unaffected
VIP unaffected IF unaffected
VIF unaffected TF unaffected
AC unaffected SF unaffected
VM unaffected ZF unaffected
RF unaffected AF unaffected
NT unaffected PF unaffected
IOPL unaffected CF unaffected
OF unaffected