Owner`s manual

Appendix F

Control Flags for Booting

With the console BOOT command, you can control various phases of booting

by setting bits in General Purpose Register R5:

BOOT /R5:n

where n is in hexadecimal notation. For example, to set bit 4 in R5 when

booting, you would enter:

BOOT /R5:10

The R5 bit functions are deﬁned by VMB and by the operating system. The

value –1 in R5 is reserved for Digital.

Table F–1: R5 Bit Functions for VMS

Bit Function

0 Conversational boot. The secondary bootstrap program, SYSBOOT, prompts you

for system parameters at the console terminal.

1 Debug. If this ﬂag bit is set, the operating system maps the code for the

XDELTA debugger into the system page tables of the running operating sys-

tem.

2 Initial breakpoint. If this ﬂag bit is set, VMS executes a breakpoint (BPT) in-

struction early in the bootstrapping process.

3 Secondary boot from boot block. The secondary boot is a single 512-

byte block whose logical block number is speciﬁed in General Purpose Regis-

ter R4.

4 Boots the VAX Diagnostic Supervisor. The secondary loader isan image calledDI-

AGBOOT.EXE.

5 Boot breakpoint. This stops the primary and secondary loaders with a break-

point (BPT) instruction before testing memory.

Control Flags for Booting F–1