Re: Direct access to hardware

From: James Sutherland (jas88@cam.ac.uk)
Date: Wed Jul 26 2000 - 10:06:45 EST


On Wed, 26 Jul 2000, Stephen Frost wrote:

> On Wed, 26 Jul 2000, James Sutherland wrote:
>
> > Trap the defective instructions, and implement a replacement instruction
> > in software. On later Intel CPUs, you can sometimes use a microcode update
> > to fix it - this also requires OS intervention.
> >
> > Either way, essentially you tell the OS to block the duff instructions,
> > and it does so.
>
> Erm, the OS basically tells the CPU to handle it, so the OS doesn't
> have to worry about it. The OS certainly doesn't sit and check every
> instruction being sent to the CPU is valid. The parallel to IDE would be
> sending an initial command to the drive saying "Don't let me touch your
> firmware" on boot and then never having to think about it again. This
> would be a relatively small patch (if it was supported by the drive) I
> suspect and probably would go in with no problem.

That's Andre's current plan, so what's the problem?

James.

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