Re: [PATCH] fix i486 boot failure due to stale %ds

[Linus Torvalds]

On Sun, 4 Nov 2007, Linus Torvalds wrote:
> 
> So I'd suggest having both jumps back-to-back, but realistically, the 
> first regular short jump is actually the one that is more important. 
> That's the one that really matters on i386/i486 class machines, and later 
> CPU's will generally do the right thing even with _neither_ jump there.

That's obviously badly phrased.

The far jump is obviously required on all CPU's in order for us to 
actually finally get to 32-bit protected mode and reload CS, but what I 
*meant* was that we certainly also know that "unreal mode" works and is 
used by various strange DOS extenders, and that not doing the far jump 
isn't really required for having a "working setup" - it's just going to be 
a rather limited mode.

So the short jump is required for the code to *work*. The long jump is 
required only to get us the 32-bit mode we *want* and out of the odd 
"half-way" state. Two different issues.

		Linus
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