 These variable-range MTRRs can be used to set the caching policy of graphics memory and other memory ranges used by PCI devices.Starting with the Intel P6 family of processors (Pentium Pro, Pentium II and later), MTRRs may be used to control the processor access to memory ranges.The Cyrix 6x86, 6x86MX and MII processors have Address Range Registers (ARRs) which provide a similar functionality to MTRRs.