Re: Memory mapped IO vs Port IO

Matthew Wilcox
2003-09-11T16:42:13Z

On Thu, Sep 11, 2003 at 06:31:36PM +0200, Andi Kleen wrote:
> On Thu, 11 Sep 2003 17:25:04 +0100
> Matthew Wilcox <willy@debian.org> wrote:
> > That's not true for MMIO writes which are posted. They should take
> > no longer than a memory write. For MMIO reads and PIO reads & writes,
> > you are, of course, correct.
>
> Even a memory write is tens to hundres of cycles.

So are mispredicted branches.

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