Re: Intel vs AMD x86-64

[Linus Torvalds]

On Mon, 23 Feb 2004, David S. Miller wrote:
> 
> You mean the PCI controller is in the CPU, else how else would you
> accomplish this?

The IOMMU basically needs to be on the northbridge or at least in between
the PCI bus an a northbridge (pretty much by definition: the bridge
between IO and memory). On an Opteron, that's on-the-chip. For current
Intel chips that's a separate chip.

In fact, I _think_ you could actually use the AGP bridge as a strange
IOMMU. Of course, right now their AGP bridges are all 32-bit limited
anyway, but the point being that they at least in theory would seem to
have the capability to do this.

> Really, not having an IOMMU on a 64-bit platform these days is basically like
> pulling out one's toenails with an ice pick.

Well, as long as they had that "64-bit is server" mentality, they can 
honestly say that you just have to use 64-bit-capable PCI cards.

Now, the "server only" mentality is obviously crap, but since we haven't
even seen the chipsets designed for the 64-bit chips, we shouldn't
complain. At least yet.

Now, I'm not above complaining about Intel (in fact, the Intel people seem
to often think I hate them because I'm apparently the only person who gets
quoted who complains about bad decisions publicly), but at least I try to
avoid complaining before-the-fact ;)

			Linus
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