Re: Direct access to hardware

From: Stephen Frost (sfrost@ns.snowman.net)
Date: Wed Jul 26 2000 - 09:00:58 EST


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.

                Stephen

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