Highly specialized instructions that can only be run with CPL = 0 - LGDT - Load GDT register If we allow this at a lower privileged level, we could allow writing the address pointer to some garbage location. - LLDT - Load LDT register Local discriptor table. LDT is for each process, GDT is common. If this could be changed at user level, we could change which locations we could go to. - LTR - Load task register - LIDT - Load IDT register - MOV (control registers) - Load and store control registers - LMSW - Load machine status word - CLTS - Clear task-switched flag in register CR0 - MOV (debug registers) - Load and store debug registers - INVD - Invalidate cache, without writeback - WBINVD - Invalidate cache, with writeback - INVLPG - Invalidate TLB entry - HLT - Halt processor - RDMSR - Read model-specific registers - WRMSR - Write mode-specific registers - RDPMC - Read performance-monitoring counter - RDTSC - Read time-stamp counter