SetWP Working Point Command

The SetWP is a command that invokes a look up table for VID set points. During the initial power on phase the CPU will program the WPx registers (WP0=3Ah..WP7=41h) on a per rail address basis. When used with the AllCall address, SetWP acts as a group command that moves all voltage rails on the bus to new voltages. The SetWP command can also be used with an individual VR rail address and that rail moves to the voltage in the loop up table index. Each VR domain address has registers WP0-WPx (3Ah..41h) which stores the VID code for that domain's work points.

The Work Point command is encoded to support up to eight VID targets, slew rate for the command, and alert function. The PWM should use its auto power state or auto-phase shedding functions to select appropriate # phases, CCM/DCM operation, and so on, based on output load current after the SetWP command target has been reached.

Typical SetWP usage will be:

1. Processor writes VID codes to WP registers WP0 (3Ah) -WP4 (3Dh) in each VR domain. Normally done during SVID enumeration phase of system boot.
2. If a WP0-7 register is not programmed by the CPU, the VR stays at its present VID setting when it receives a SetWP (WPn) command.
3. Processor sends SetWP (WPn) command to one of the AllCall addresses 0Eh or 0Fh. See PWM guideline for more information on AllCall address mapping.
4. Voltage rails change VID to their corresponding VID code stored in their WPx register.
5. CPU polls each VR addresses reading stutus1 to clear the alerts from the VRs.
6. SVID error handling described in Serial VID Interface (SVID) Signals

WP0 = State 0, programed by master

WP1 = State 1, programmed by master

WP2 = State 2, programmed by master

WP3 = State 3, programmed by master

WP4 = State 4, programmed by master

...

WP7 = State 7

For the 4th Gen Intel® Xeon® Processor Scalable Family, Codename Sapphire Rapids, SetWP1 and SetWP2 commands are used.