From: "William Case" <billlinux@xxxxxxxxxx>
Hi;
Sorry for taking up your time, but you have set me on the trail to a
couple of things I would like to understand.
> Don't mistake shortcuts used for an example for stupidity.
OK.
To be more accurate about the BIOS question; one of the things that has
always bothered me -- and it may be a result of stupidity -- is when I
turn on my computer in a cold boot, power first flows to the main BIOS
(read Firmware Hub for Intel) and then to the other auxiliary BIOSes.
E.g. something has to turn on, nudge or elbow the video BIOS, probably
even before POST is begun (I will check the exact timing), so that video
BIOS can start the video card in order for the Monitor to show the LOGO
screen or if interrupted the BIOS setup screen. The LOGO screen and
setup screen are in main BIOS flash memory -- aren't they?
How does main BIOS, at this early stage, know were the auxiliary BIOSes
are and which ones to elbow into action -- this is after all before PnP
has kicked in?
This is the subject of many standards. There is an open source bios
project. You may find some specific answers there. (I don't know their
address, though.)
The interpreters are very simple, too. Check out a copy of the source for
the VERY old "TinyBASIC" interpreter. Or find one of the copies for the
disassembled and recreated source for Commodore BASIC. It takes time to
get a handle on it. But you can see how it parses and executes rather
than parses and translates. A BASIC interpreter sometimes includes specific
lexical passes, translation to an internal code representation, and
execution, via translation, of the internal code representation. Often the
translation is a jump table. (I learned by creating my own source for an
HP BASIC interpreter that was handy. Darned fine code in it, too.)
You know, to get a real answer I am probably going to have to slog my
way through the BASH source code. Ruefully; I would have thought that
someone would have already done the slogging and left a nice neat
readable explanation for the world. Oh well.
Happy slogging. {o.o}
Simpler CPUs are easier to grasp at first. That's why textbooks with their
simplifications can help. Lacking textbooks the 68000 manuals, hardware
and software, can illuminate a LOT of important concepts.
{^_^}
Yea, my neighbour has a basement full of 68000 textbooks and manuals.
Hey, I said 68000. And I did mean the Motorola books. That's basically
two manuals in various forms. Forget about the follow on chips if you are
simply learning concepts. The key MIGHT be in the programming manual.
It shows how register is encoded in the commands very clearly.
{^_^}
