Table 10–1 : Unprivileged Digital UNIX PALcode Instruction Summary (Continued)

Mnemonic

Operation and Description

 

 

rdunique

Read unique

 

The rdunique instruction returns the process unique value.

urti

Return from user mode trap

 

The urti instruction pops from the user stack the registers a0 through a2, the

 

global pointer, the new user assembler temporary register, the stack pointer, the

 

program counter, and the processor status register.

wrunique

Write unique

 

The wrunique instruction sets the process unique register.

 

 

10.2 Privileged Digital UNIX PALcode

The privileged PALcode instructions can be called only from kernel mode. They provide an interface to control the privileged state of the machine.

Table 10–2describes the privileged Digital UNIX PALcode instructions.

Table 10–2 : Privileged Digital UNIX PALcode Instruction Summary

Mnemonic

Operation and Description

 

 

cflush

Cache flush The cflush instruction flushes an entire physical page pointed to by

 

the specified page frame number (PFN) from any data caches associated with

 

the current processor. All processors must implement this instruction.

cserve

Console service This instruction is specific to each PALcode and console

 

implementation and is not intended for operating system use.

draina

Drain aborts The draina instruction stalls instruction issuing until all prior

 

instructions are guaranteed to complete without incurring aborts.

halt

Halt processor The halt instruction stops normal instruction processing.

 

Depending on the halt action setting, the processor can either enter console

 

mode or the restart sequence.

rdmces

Read machine check error summary The rdmces instruction returns the MCES

 

register in v0.

rdps

Read processor status The rdps instruction returns the current PS.

rdusp

Read user stack pointer The rdusp instruction reads the user stack pointer while

 

in kernel mode and returns it.

rdval

Read system value The rdval instruction reads a 64-bit per-processor value and

 

returns it.

 

 

10–2Alpha Architecture Handbook

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Compaq ECQD2KCTE manual Privileged Digital Unix PALcode