Re: alpha iommu fixes

[Andrea Arcangeli]

On Mon, May 21, 2001 at 03:11:52AM -0700, David S. Miller wrote:
> I think such designs which gobble up a gig or so of DMA mappings on

they maps something like 200mbyte I think. I also seen other cards doing
the same kind of stuff again for the distributed computing.

> to be using dual address cycles, ie. 64-bit PCI addressing.  It is
> the same response you would give to someone trying to obtain 3 or more
> gigabytes of user address space in a process on x86, right?  You might

I never seen those running on 64bit boxes even if they are supposed to
run there too.

Here it's a little different, 32bit virtual address space limitation
isn't always a showstopper for those kind of CPU intensive apps (they
don't need huge caches).

> respond to that person "What you really need is x86-64." for example
> :-)

for the 32bit virtual address space issues of course yes ;)

> To me, from this perspective, the Quadrics sounds instead like a very
> broken piece of hardware.  And in any event, is there even a Quadrics

they're not the only ones doing that, I seen others doing that kind of
stuff, it's just a matter of information memory fast across a cluster,
if you delegate that work to a separate engine (btw they runs a
sparc32bit cpu, also guess why they aren't pci64) you can spend much
more cpu cycles of the main CPU on the userspace computations.

> driver for sparc64? :-)  (I'm a free software old-fart, so please
> excuse my immediate association between "high end" and "proprietary"
> :-)

:)

Andrea