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10–1
Chapter 10
Digital UNIX
The following sections specifiy the Privileged Architecture Library (PALcode) instructions that are
required to support a Digital UNIX system.
10.1 Unprivileged Digital UNIX PALcode
Table 10–1 describes the unprivileged Digital UNIX PALcode instructions.
Table 10–1 : Unprivileged Digital UNIX PALcode Instruction Summary
Mnemonic Operation and Description
bpt Break point trap
The bpt instruction switches mode to kernel, builds a stack frame on the kernel
stack, and dispatches to the breakpoint code.
bugchk Bugcheck
The bugchk instruction switches mode to kernel, builds a stack frame on the
kernel stack, and dispatches to the breakpoint code.
callsys System call
The callsys instruction switches mode to kernel, builds a callsys stack frame,
and dispatches to the system call code.
clrfen Clear floating-point enable
The clrfen instruction writes a zero to the floating-point enable register.
gentrap Generate trap
The gentrap instruction switches mode to kernel, builds a stack frame on the
kernel stack, and dispatches to the gentrap code.
imb I-stream memory barrier
The imb instruction makes the I-cache coherent with main memory.