AW: AW: [Fwd: Re: EDE - Personal Suggestions and Ideas]

Mario Premke
2004-05-26T11:43:03Z

> > Particularly, on systems that don't have an MMU, the segment ID
> controls the
> > address of the segment; so on the 8086 and 8088 you won't be
> able to move
> > your application's segments around while the program's running.
>
> Why? On 16 bit protected mode (80286) you CAN alter the starting
> address of
> a segment while refeering the same selector before and after this action
> (this is because in protected mode the segment register only contains a
> 'selector' which is an index in the descriptor table which describes the
> segment). Sure, real mode does not allow this, because in real mode the
> content of the segment register is simply the starting address of the
> segment divided by 16, allowing maximum of 1Mb address space

Is it possible to use the the content of the segment register in real mode
as a selector in protected mode - so assuming GDT and possibly LDT are
properly set up, would a real mode program run in protected mode?

>
> Yep, but if you don't want to buy +386 system, and you wanna to provide
> the possibility to run a Linux-like OS on 8086 and 286 you should
> deal with
> them ...
>
Yes, that's what I meant, because these CPU's are very limited, every
possible feature should be supported.

Mario