[mythtv-users] Strange Ceton issues.

[Larry Finger]

On 08/04/2011 10:31 AM, Erik Jensen wrote:

> Well, maybe, but it works fine on my AMD 64-bit machine with 16 GiB of
> RAM, so there must be at least one other piece to the puzzle.

If the device only supports 32-bit DMA addressing, then a 64-bit kernel and a 
PAE kernel have the same issues: The DMA buffers must have a physical address in 
the lowest 4GB of RAM. I have no idea why it should work with 3 GB and not with 
4. That makes no sense.

The tricky part is when you are dealing with ISA devices with 24-bit addressing, 
or some PCI devices with 30-bit addressing. Finding low memory that satisfies 
these conditions is harder.

As the DMA APIs are not that hard to follow, only Erik's observation seems to be 
sensible.

Larry