On I64 systems, specifies control registers %CR0 through %CR81,
    as follows:

    Register
    Symbol         Definition

    %CR0           Default control
    %CR1           Interval timer match (SCD only)
    %CR2           Interruption vector address (SCD only)
    %CR8           Page table address (SCD only)
    %CR16,%IPSR    Interruption processor status
    %CR17          Interruption status
    %CR19          Interruption instruction pointer
    %CR20          Interruption faulting address
    %CR21          Interruption TLB insertion
    %CR22          Interruption instruction previous
    %CR23          Interruption function state
    %CR24          Interruption immediate
    %CR25          Interruption hash address
    %CR64          Local interrupt ID (SCD only)
    %CR66          Task priority (SCD only)
    %CR68 -        External interrupt request 0 to 3 (SCD only)
    %CR71
    %CR72          Interval timer (SCD only)
    %CR73          Performance monitoring (SCD only)
    %CR74          Corrected machine check vector (SCD only)
    %CR80 . . .    Local redirection 0 and 1 (SCD only)
    %CR81