[Beowulf] Supermicro 2U

[Greg Lindahl]

On Mon, Feb 23, 2009 at 08:30:24AM -0800, Lucas Sheehan wrote:

> Is there really that much effect from a riser or other connector?

There was in the PCI/PCI-X era -- sometimes you had to downclock the
bus (a BIOS option) to get it to work reliably. And it was very
important to use a riser which was tested by the mobo manufacturer.

I've never seen PCIe screw that up, which is good, because you can't
clock it down. And in theory the risers are interchangable, because
the noise budget in the standard allows for risers.  If you did have
significant signal integrity problems, you're likely to get an
uncorrectable error, which should halt the system.

-- greg