Datasheet

Processor Configuration Registers
16 Datasheet, Volume 2
RW-V-L
Read/Write/Volatile/Lockable bit(s). These bits can be read and written by software.
Hardware may set or clear the bit based upon internal events, possibly sooner than any
subsequent software read could retrieve the value written. Additionally, there is a bit (which is
marked RW-K or RW-L-K) that, when set, prohibits this bit field from being writable (bit field
becomes Read Only).
RW-V-L-S
Read/Write/Volatile/Lockable/Sticky bit(s). These bits can be read and written by
software. Hardware may set or clear the bit based upon internal events, possibly sooner than any
subsequent software read could retrieve the value written. Additionally, there is a bit (which is
marked RW-K or RW-L-K) that, when set, prohibits this bit field from being writable (bit field
becomes Read Only). These bits return to their Reset Values on cold reset.
RW-S
Read/Write/Sticky bit(s). These bits can be read and written by software. Bits are not
returned to their Reset Values by “warm” reset, but will return to Reset Values with a
cold/complete reset (for PCI Express related bits a cold reset is “Power Good Reset” as defined in
the PCI Express spec).
RW-O
Read/Write Once bit(s). Reads prior to the first write return the Reset Value. The first write
after warm reset stores any value written. Any subsequent write to this bit field is ignored. All
subsequent reads return the first value written. The value returns to default on warm reset. If
there are multiple RW-O or RW-O-S fields within a DWORD, they should be written all at once
(atomically) to avoid capturing an incorrect value.
RW-O-S
Read/Write Once/Sticky bit(s). Reads prior to the first write return the Reset Value. The first
write after cold reset stores any value written. Any subsequent write to this bit field is ignored. All
subsequent reads return the first value written. The value returns to default on cold reset. If
there are multiple RW-O or RW-O-S fields within a DWORD, they should be written all at once
(atomically) to avoid capturing an incorrect value.
W
Write-only. These bits may be written by software, but will always return zeros when read. They
are used for write side-effects. Any data written to these registers cannot be retrieved.
W1C
Write 1 to Clear-only. These bits may be cleared by software by writing a 1. Writing a 0 has no
effect. The state of the bits cannot be read directly. The states of such bits are tracked outside
the processor and all read transactions to the address of such bits are routed to the other agent.
Write transactions to these bits go to both agents.
MBZ Must Be Zero when writing this bit.
Table 2-1. Register Terminology (Sheet 2 of 2)
Item Description