fetcher:

     NOP
     IN AL,port   ; Note that this corrupts EAX...
     MOV TR5,EBX  ; EBX contained the new TR5 value.
     NOP
     NOP

On the A to C0 step of the 486 loading a value into CR0 which disables the
cache may corrupt the cache. Forcing a prefetch will avoid this.

     PUSHFD
     CLI
     MOV BL,CS:label
     MOV CR0,EAX