6. System Interface Operations
2-bit user-defined Uncached Attribute, which is driven on SysAD[59:58] during the address cycle of the following:
- processor double/single/partial-word read requests
- double/single/partial-word write requests
- block write requests resulting from completely gathered uncached accelerated blocks
For unmapped accesses, the uncached attribute is sourced from VA[58:57].
For mapped accesses, the uncached attribute is sourced from the TLB Uncached Attribute field. The TLB Uncached Attribute field may be initialized in 64-bit mode using bits 63:62 of the CP0 EntryLo0 and EntryLo1 registers.