> On the coutrary, e.g. Solaris handles > 4GB memory fine - it "just
> works", without need for special calls in applications.  (I've not
> tried this, but Sun writes this in their docs).

Probably does - mind you the number of 'abstraction layers' between a
solaris device driver and the hardware has to be seem to be believed.

Any driver trying to do dma into a buffer above 4G will find the dma_map()
will fail.

I wonder how they to disk i/o into this memory?

Is it possibly to remap the DRAM banks (ie in a different order) on the
fly to make this work?
(cf the way your physical memory ends up contiguous on a PC regardless
of which SIMM slots you fill)

    David