access control register การใช้

• Within a virtual machine, code can run at up to sixteen different layers of protection, called access levels ( or ACR levels, after the Access Control Register which controls the mechanism ).
• Independently, an array of 256 2-bit "'access control registers "'for the first 128k words of "'real "'memory function as a " lock-and-key " system in conjunction with two bits in the program status doubleword.
• It had the advantage that as the last large-scale operating system ever designed, and one built from scratch, its underlying architecture encompassed many of the primitives needed to develop a Secure System, in particular the hardware assisted Access Control Registers ( ACR ) to limit to privileges that could be taken by any process ( including Users ).