Re: Railways and the Millennium Bug

[Alex Borodin <alex.borodin@qr.com.au>]

Geoff Lambert wrote:
> 
> "Chris Stratton" <stratton.chris.cp@bhp.com.au> wrote:
> 
> >I would argue that BIOS is software that is stored in ROM. Quoting from one

Sure.. it definitely _IS_ software stored in ROM... which is often 
referred to as "FIRMWARE", which is the term I used. No need to argue!

> Well, this is only partly true.   The greater part of the BIOS usually
> resides in the file IO.SYS, a disk file.  In addition, you may write
> your own device drivers, which exist as separate files.  System start
> in DOS begins with at address 0FFFF0H, which IS in ROM, this in turn
> calls the bootstrap routine which is also in ROM.  This in turn calls
> the disk bootsrap routine that is NOT in ROM.  In turn, this loads
> IO.SYS (the BIOS) from disk and, at some stage (perhaps) integrates
> those bits of the BIOS that usually ARE in ROM (usually the very
> fundamental bits).  After that, it gets hairier, invlving things like
> SYSINT which usually are on disk, but are linked to some ROM code.
> 
> Boiling this down: for DOS systems at least, the proportion of BIOS
> that resides in ROM can be 0.0 to 1.0.

The original point of the discussion was "the Millenium Bug" and I 
was merely attempting to illuminate the main source of this "bug".

The portion of the BIOS firmware which handles the system clock in 
most PC systems is stored in ROM, as it is an extremely basic
function.


-- 
Alex Borodin - Software and Systems Engineer - Queensland Rail
Ph: +61-7-3235-2482  Fax:+61-7-3235-2747
"He shall deliver thee in six troubles: yea, in seven 
there shall no evil touch thee." - Job 5:19