Continual reading from the PowerPc time base register is not stable

[Benjamin Herrenschmidt]

On Thu, 2010-03-25 at 16:00 -0600, Chris Friesen wrote:
> Shouldn't "upper" be cast to 64-bit before shifting?

Yup but that doesn't explain his results. I think Segher nailed it to a
stuck bit tho, so I would blame defective HW or HW used outside of
normal operating conditions (maybe the TB is sourced out of bounds ?)

Cheers,
Ben.