With continuing apologies to those objecting to the added time required for
their mail downloads, here is the next installment:
<quote>
ANDY wrote:
>
> > Re: Do something quick. There is no way with a PC of any vintage to enter
> > binary instructions directly to memory to form a program. There is no
> > switchpanel. And the instructions MUST be in memory. I may have misguided
> > you when I said something like: "present the instuctions to the machine".
>
> you said the *OS* presents instructions to the chip/machine
>
> >
> > Actually, the machine LOOKS for instructions in memory.
>
> It looks where you
> ^^^^^ ^^^
> ?-- WHERE?? would *I*?? tell the machine "where to look for the FIRST
> instruction" *WITHOUT*!! DOS???
An excellent question Andy.
We have come to think of the PC as a machine that is dead without DOS.
That isn't true. The PC as a machine exists on two levels UNDER (without)
an OS like DOS or Linux. The first, and most primitive level is the actual
hardware. The CPU has a built-in instruction set and is internally pre-
configured to look at the highest address in normal memory (the 1Mb limit)
for it's FIRST instruction.
If you have the necessary hardware information regarding address and data
buss pinouts for the ISA or PCI slots, you can rig some logic and a switch
panel for the CPU to read it's first instruction from. That isn't much
good unless you have further instructions for it, so instead of a switch
panel you could mount a programmable memory chip on a card that might be
programmed with whatever machine instructions you like. Flash the lights
blow the horn, spin the wheels, or read instructions from the keyboard or
even a floppy drive or hard disk.
So the above is the naked machine. It will do absolutely nothing unless
you personally provide the binary instructions AND information in the
very first instruction about where to look for the second one ! The only
way to do this is to connect something electrically to the address/data
buss.
The second level does the above job for you - but it does the job in a
very specific way. While YOU could have made the machine do ANYTHING,
the BIOS chip is a memory device that interfaces to the address/data
busses at high memory and does a specific job. It tells the machine to
look at the hardware configuration in CMOS and then try to load some
form of program (it COULD be an operating system but it doesn't have
to be) to enable the machine to do something even MORE complicated.
And so on. Each level allows for the possibility of more complex
operations. HARDWARE <BIOS <DOS <WINDOWS <NETSCAPE <JAVA etc.
> or do you mean DOS as my instrument...
Could be. If you choose to have DOS start your program which you have in a
.COM file, DOS will load the program into memory and then tell the machine
where to look to start it.
> > (or DOS) tells it to look for the FIRST instruction, and then it proceeds
> ^^^^^^
> > in an orderly manner sequentially through memory until the result of an
> > instruction tells it to go somewhere else. (Branch)
> >
> > So, you must somehow get the instructions into memory. There is no way to
> > do this from the keyboard.
>
> ? Is there any way to do it without DOS??
Yes. The BIOS executes long before DOS is loaded. In fact, it loads DOS
as one of its jobs. You can replace the BIOS if you wish to have a pure
machine at your disposal. But then YOU have to do everything. And you must
have a lot of technical information at your disposal. <g>
> So what you are saying is: I *MUST* have an OS like DOS - , irregardless
> of whether or not I use DEBUG.EXE, - to "present" ANY assembly or hex
> (yet no matter what; NOT ones and zeros binary) instructions to the
> chip/machine of ANY PC
>
> that the bottom line is: that I *Need* *DOS* to create and run these
> programs (: and that without DOS, these assembly and hex programs can't be
> created or run... (:
No, I'm definitely NOT saying that. It all depends on how basic you want
to get. You can create a program by programming individual bytes in an
EPROM with an Eprom Programmer. There were some older versions that had
switch banks for that purpose. Then you can replace the bios chip with
your eprom and the machine will run your program instantly upon power-on.
I know you don't really want to do that of course. This is all for the
purpose of discussion only.
Yes ?
In reality, we would all rather skip the details and just use DOS to do
the dirty work I think. <G>
</quote>
Before someone calls me on this point, where I said "The BIOS executes long
before DOS", I should have been more clear and said that PORTIONS of the bios
execute before DOS is loaded. Like the "Power On Self Test" and "Bootstrap".
Other parts of the BIOS may be called upon later by DOS, as it is the bios,
and ONLY the bios, that knows anything about your motherboard.
Well, maybe YOU know something about it too. <G>
- Clarence Verge
--
- Help stamp out FATWARE. As a start visit: http://home.arachne.cz/
- The internet is infected - Windows is a VIRUS !!
--
