User`s guide

B.1 SROM Initialization
9. Scan the system flash ROM for a special header that specifies where and
how the system flash ROM firmware should be loaded.
10. Copy the contents of the system flash ROM to memory and begin code
execution.
11. Pass parameters up to the next level of firmware to provide a predictable
firmware interface.
B.2 Firmware Interface
A firmware interface provides a mechanism for passing critical information
about the state of the system and CPU up to the next level of firmware.
This interface is achieved through the use of a set of defined SROM output
parameters as described in Table B–1
This specific firmware interface serves the 21164 microprocessor. Other Alpha
microprocessor implementations require a different firmware interface.
Table B–1 Output Parameter Descriptions
Output Parameter Parameter Description
r1 (t0)—BC_CONTROL
value
The BC_CONTROL value allows the next-level software
to preserve any system-specific Bcache configuration
information.
r2 (t1)—BC_CONFIG value The BC_CONFIG value preserves the Bcache
configuration information such as, size and read/write
speed.
r3 (t2)—BC_CONFIG_OFF
value
The BC_CONFIG value for turning the Bcache off, if
necessary. This value may be harder to be determined
by the next level of firmware, so the SROM computes it
and passes it up.
r17 (a1)—Memory size This value is an unsigned quadword count of the
number of contiguous bytes of good memory in the
system starting at physical address zero. This simple
mechanism is sufficient for simple systems. Systems
that need to communicate more detailed memory
configuration can do so through the system context
value (see last entry in this table).
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B–2 SROM Initialization