Re: AdaOS

[Mats Karlssohn <mats@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
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