System instructions

Name	Description	Code	Operation	operands	operand size
System instructions
lmsw	Load machine status word	lmsw source	Loads source into machine status word of CR0(bits0-15)	reg mem	word
smsw	Store machine status word	smsw dest	Store machine status word to dest	reg mem	word
lgdt	Load global descriptor table (GDT) register	lgdt source	Load source into GDTR	mem	pword
sgdt	Store global descriptor table (GDT) register	sgdt dest	Store GDTR to dest
lidt	Load interrupt descriptor table (IDT) register	lidt source	Load source into IDTR
sidt	Store interrupt descriptor table (IDT) register	sidt dest	Store IDTR to dest
lldt	Load local descriptor table (LDT) register	lldt source	Load segment selector source into LDTR	reg mem	word
sldt	Store local descriptor table (LDT) register	sldt dest	Stores segment selector from LDTR in dest	reg mem	word
ltr	Load task register	ltr source	Load source into task register	reg mem	word
str	Store task register	str dest	Stores segment selector from TR in dest	reg mem	word
lar	Load access rights	lar dest,source	load access rights from segment descriptor specified by the selector in source into dest and set ZF	reg,reg reg,mem	word dword
lsl	Load segment limit	lsl dest,source	load segment limit from segement descriptor specified by selector in source int dest and set ZF	reg,reg reg,mem	word dword
verr	Verify segment for reading	verr op	SET ZF=1 if segment specified with op can be read	reg mem	word
verw	Verify segment for writing	verw op	SET ZF=1 if segment specified with op can be written	reg mem	word
arpl	Adjust requested privilege level	arpl op1,op2	Adjust RPL of op1 to not less than RPL of op2	reg,reg mem,reg	word
clts	Clear the task-switched flag	clts	Clears TS flag in CR0
lock	Lock Bus	lock	Asserts LOCK# signal for duration of the accompanying instruction
hlt	Halt processor	hlt	Halt
invlpg	Invalidate TLB Entry	invlpg m	Invalidate TLB Entry for page that contains m	mem
invd	Invalidate cache, no writeback	invd	Flush internal caches; initiate flushing of external caches.
wbinvd	Invalidate cache, with writeback	wbinvd	Write back and flush Internal caches; initiate writing-back and flushing of external caches.
rdpmc	Read performance monitoring counters	rdpmc	Read performance-monitoring counter specified by ECX into EDX:EAX
rdtsc	Read time stamp counter	rdtsc	Read time-stamp counter into EDX:EAX
rsm	Return from system management mode (SSM)	rsm	Resume operation of interrupted program
rdmsr	Read model-specific register	rdmsr	Load MSR specified by ECX into EDX:EAX
wrmsr	Write model-specific register	wrmsr	Write the value in EDX:EAX to MSR specified by ECX
sysenter	Fast System Call, transfers to a flat protected mode kernel at CPL=0.	sysenter	Fast call to privilege level 0 system procedures
sysexit	Fast System Call, transfers to a flat protected mode kernel at CPL=3.	sysexit	Fast return to privilege level 3 user code