Compaq ECQD2KCTE Windows NT Alpha Functions and Argument, Input Contents Register Bits Meaning

For the Windows NT Alpha Operating System

When a counter overflows and interrupt enabling conditions are correct, the counter causes an interrupt to PALcode. The PALcode builds a frame on the kernel stack and dispatches to the kernel at the interrupt entry point.

E.2.2.2 Windows NT Alpha Functions and Argument

The functions for Windows NT Alpha execute on only a single (the current running) processor. The wrperfmon instruction is called with the following input registers:

Input Contents

Register (Bits) Meaning

a0	63–0
a1	0

The register in Table E–3,which contains the value to be written to the hardware PMCTR register.

When a1 = 0, write a0 to the hardware PMCTR register.

When a1 = 1, read the hardware PMCTR register. The returned PMCTR register is written to register v0.

a2	2–0	Has meaning when PCSEL1 in Table E–3has the value 0xF. Con-
		tents are determined by processor type:
		Processor	Contents	Reference
		21164	CBOX1	Table E–15
		21164PC	PM0_MUX	Table E–17
a3	2–0	Has meaning when PCSEL2 in Table E–3has the value 0xF. Con-
		tents are determined by processor type:
		Processor	Contents	Reference
		21164	CBOX2	Table E–16
		21164PC	PM1_MUX	Table E–18

E–10Alpha Architecture Handbook