From: Wilkinson,Alex (Alex.Wilkinson@dsto.defence.gov.au)
Date: Mon May 20 2002 - 23:59:40 EDT
Thanks to:
"Dr. Thomas.Blinn@Compaq.com" <tpb@doctor.zk3.dec.com>
"Thursday" AKA dr. john <thursday@allidaho.com>
"Monica Fernndez Pereiro" <monica.fernandez@proinfor.com>
Chris Bryant <cbryant@dollar.com>
alan@nabeth.cxo.cpqcorp.net
Original Question
-----------------
> Hi all,
>
> A couple of quick questions:
>
> - What is the difference between the SRM, AlphaBIOS and ARC ?
>
> - What is PALcode ?
Answer:
------
SRM stands for "Systems Reference Manual" or more accurately the
Alpha SRM in the case of Alpha systems (there was a VAX SRM for
the VAX systems that preceded Alpha). The real SRM is restricted
distribution and contains details that specify many features of
Alpha systems. The console firmware written to implement those
features specified in the SRM is often refered to as the SRM
console.
ARC stands for "Advanced RISC Console", one of the few results of
the Advanced Computing Environment (ACE) initiative. It was the
console defined by Microsoft and system partners to support the
RISC based Windows NT implementations. I suspect that it was on
MIPS hardware, there was an implementation for Alpha systems, it
could have been implemented on any reasonably modern RISC based
system.
AlphaBIOS is the BIOS emulation software that's implemented in the
Alpha SRM console. Some ISA, EISA, or PCI options require that at
least some BIOS compatible interfaces be present in order to work
correctly, and AlphaBIOS is the software that provides the features
that are needed. It may also provide an implementation of the
ARC environment on some systems.
PAL is the Privileged Architecture Library, as defined in the Alpha
SRM; it implements routines that run uninterruptibly and that can
extend the basic Alpha hardware instruction set to provide things
that need to be done at a very low level, almost in hardware. It
is delivered in the SRM console firmware, and the details of what
it does can vary among CPU architecture revisions (e.g., EV4, EV5,
EV6, EV7). PAL knows a lot of details about the chip hardware, so
it provides an abstraction so system software doesn't need to have
the details of every chip. It plays a key role in such things as
memory management, I/O interrupt handling, and so on.
There are books about the Alpha architecture that explain some of
this reasonably well; some parts aren't well documented outside of
the "restricted" SRM or the code itself.
- Alex
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