Vax 613 0S Instruction Manual Page 209

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Table 48 (Cont.) Register Values After Power-Up
Name Value Description
I/O Controllers
SCC0, SCC1 Mouse and keyboard port are 4800 baud while
communications and printer port are 9600
baud. All ports have 8-bit character, one stop
bit, parity off.
SCSI The SCSI controllers are reset by issuing a
Reset Chip command to each controller. The
controller registers are left in the reset state.
Memory
0x00000000 All memory not loaded by the boot code is
initialized to a pattern of 0x00000000.
14.5 System Firmware Entry
System firmware refers to the software loaded from the SYS ROM and I/O ROM
by the software in the SROM. It contains the main console software, PALcode,
and diagnostics.
The system firmware checks for a power-on entry to see if the power-on self-test
should be executed. If system firmware finds no power-on entry, it passes control
to the dispatch code described in Example 2, which uses the halt code set by the
hardware at entry. The halt action fields, restart in progress and bootstrap in
progress bits are stored in the HWRPB.
14.5.1 Restart
The restart operation is restarted at an address specified in the HWRPB. The
HWRPB ‘‘restart in progress’’ flag is used to avoid repeated attempts to restart a
failing operating system. A system restart can occur as the result of a processor
halt. Section 16.5 discusses the HWRPB.
14.5.2 Boot
System firmware can load and start (bootstrap) an operating system. To do so,
it attempts to load the secondary bootstrap code from the device specified in the
BOOT command or from the boot device environment variable, if no device is
entered at the console prompt.
These actions occur when system software is booted:
1. Build a copy of HWRPB data structures for the operating system
2. Map these data structures and the firmware, so they reside in the boot
address space specified by the Alpha Architecture Handbook.
3. Load system software
4. Initialize processor state
5. Transfer control to system software
Powerup Initialization and Firmware Entry 14–9
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