Re: AdaOS

["Brian Catlin" <brianc@sannas.org>]

The HAL is essentially the driver for the motherboard, and controls the
interrupt controller, DMA controller, timer, etc.  The HAL used to contain the
bus drivers through NT4, but starting with Windows 2000, the bus drivers were
migrated out of the HAL and into standalone drivers, reducing the need for OEMs
to create their own HALs (most were created to deal with PCI controllers and
non-Intel core logic).  The kernel is processor architecture specific (there is
a different kernel for each supported architecture, x86, Alpha, PPC, MIPS,
Itanium), while the executive is the same across all platforms.

 -Brian

--
Brian Catlin, Sannas Consulting 310-798-8930
Windows NT/2000 Internals, WDM Device Driver Training & Consulting
See WWW.AZIUS.COM for courses and scheduling

"Mats Karlssohn" <mats@mida.se> wrote in message
news:3BF019F4.C9C460E5@mida.se...
> Ted Dennison wrote:
> >
> > In article <9scke6$12jb14$1@ID-25716.news.dfncis.de>, Nick Roberts says...
> > >
> > >Yes, but Phil, it's not the actual bits of software that are redundant --
> > >I've no doubt they indeed do useful things -- it's the term 'HAL' that's
> > >redundant. The hardware abstraction layer IS the device drivers, and always
> > >has been. Someone's just invented a fancy name, that's all!
> >
> > I think there's a bit more to it than that. I believe its purpose initially
was
> > to shelter the kernel from processor implemenation details, so that only the
HAL
> > would have to be rewritten to support a new processor. In that respect, you
can
> > kind of think of it as a microkernel.
>
> As usual you are quite right Ted. Please correct me if I'm workn, but I've
> been led to belive that in NT the main purpose of the HAL is to isolate the
> device drivers from the architectural differenses of of different processors
> and machines. Like the difference between the separate I/O addresspace of
> the x86 vs. {alpha,mips} memory mapped I/O, the idea is that the same device
> driver can be used for a card, it doesn't matter weather the card is in
> a AlphaStation or an Intel box. There is more to it though (as usual).
>
>
>
> --
> Mats Karlssohn, developer                         mailto:mats@mida.se
> Mida Systemutveckling AB                          http://www.mida.se
> Box 64, S-732 22 ARBOGA, SWEDEN
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