4 ms·

x86 has LOADALL and SAVEALL. https://en.wikipedia.org/wiki/LOADALL https://en.wikipedia.org/wiki/LOADALL

• msla 8y ago
  Those undocumented instructions don't exist on x86_64, and they could be used to do bizarre things on the processors which had them: > As the two LOADALL instructions were never documented and do not exist on later processors, the opcodes were reused in the AMD64 architecture.[8] The opcode for the 286 LOADALL instruction, 0F05, became the AMD64 instruction SYSCALL; the 386 LOADALL instruction, 0F07, became the SYSRET instruction. These definitions were cemented even on Intel CPUs with the introduction of the Intel 64 implementation of AMD64.[9] [snip] > Because LOADALL did not perform any checks on the validity of the data loaded into processor registers, it was possible to load a processor state that could not be normally entered, such as using real mode (PE=0) together with paging (PG=1) on 386-class CPUs.[7]
  • scandinavian 8y ago
    What about PUSHAD and POPAD for x86, those are not undocumented right?
    • jamieiles 8y ago
      There is no pusha in long mode though, you need to push individual regs.