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9–1
Chapter 9
OpenVMS Alpha
The following sections specify the Privileged Architecture Library (PALcode) instructions, that are
required to support an OpenVMS Alpha system.
9.1 Unprivileged OpenVMS Alpha PALcode
The unprivileged PALcode instructions provide support for system operations to all modes of opera-
tion (kernel, executive, supervisor, and user).
Table 9–1 describes the unprivileged OpenVMS Alpha PALcode instructions.
Table 9–1 : Unprivileged OpenVMS Alpha PALcode Instruction Summary
Mnemonic Operation and Description
BPT Breakpoint
The BPT instruction is provided for program debugging. It switches the pro-
cessor to kernel mode and pushes R2..R7, the updated PC, and PS on the ker-
nel stack. It then dispatches to the address in the Breakpoint vector, stored in a
control block.
BUGCHK Bugcheck
The BUGCHK instruction is provided for error reporting. It switches the pro-
cessor to kernel mode and pushes R2..R7, the updated PC, and PS on the ker-
nel stack. It then dispatches to the address in the bugcheck vector, stored in a
control block. The value in R16 specifies the particular bugcheck type.