Compaq ECQD2KCTE manual OpenVMS Alpha and Digital Unix Functions and Arguments, Modeselect, PCSEL1

Table E–3: Bit Summary of PMCTR Register for Windows NT Alpha (Continued)

Bits	Name	Meaning
9–8	MODE_SELECT1	Select modes in which to count:
		Value	Meaning
		0	Count all modes
		1	Count PALmode only
		2	Count all modes except PALmode
		3	Count only user mode
7–4	PCSEL1	Counter 1 selection. See Table E–13
3–0	PCSEL2	Counter 2 selection. See Table E–14

1Windows NT Alpha uses bits 30 and 9–8 differently than as documented in the 21164 Hard- ware Reference Manual; it uses the processor executive mode to run user (nonprivileged) code. Therefore, bit 30 is always set to one and bits 9–8 are used to select the mode.

E.2.2.3 OpenVMS Alpha and DIGITAL UNIX Functions and Arguments

The functions execute only on a single (the current running) processor and are described in Table E–4.

The OpenVMS Alpha MTPR_PERFMON instruction is called with a function code in R16, a function-specific argument in R17, and status is returned in R0.

The DIGITAL UNIX wrperfmon instruction is called with a function code in a0, a function specific argument in a1, and status is returned in v0.

Table E–4: OpenVMS Alpha and DIGITAL UNIX Performance Monitoring Functions

Function Register Usage		Comments
Enable performance monitoring; do not reset counters
DIGITAL UNIX
Input:	a0 = 1	Function code value
	a1 = arg	Argument from Table E–5
Output:	v0 = 1	Success
	v0 = 0	Failure (not generated)
OpenVMS Alpha
Input:	R16 = 1	Function code value
	R17 = arg	Argument from Table E–5
Output:	R0 = 1	Success
	R0 = 0	Failure (not generated)

E–12Alpha Architecture Handbook