[Beowulf] DIMMnet-1 DIMM slot NIC?

Keith D. Underwood kdunder at sandia.gov
Mon Jul 26 05:34:37 PDT 2004

The memory slot just isn't the right place for an interface anymore. 
Back in the days when PCI meant PCI 32/33, then maybe it was a good
idea.  Now, with Hypertransport available and PCI-Express emerging, the
memory slot just has too many drawbacks.  Among them:

-no interrupts:  yeah, you don't want to use interrupts if you don't
have too, but having a card with no interrupt capability is a little

-bandwidth:  For large messages, you can't get real bandwidth because a
card in the memory slot cannot master the memory bus and cannot DMA data
into the memory system (i.e. memory in another memory slot).  This means
you have to copy all of the data by getting the processor involved.

Now, if you want to implement something like UPC or SHMEM and you have
all of the shared address space located on the card plugged into that
slot (maybe not incredibly practical, but probably possible) then a DIMM
interface may be your best bet.


On Sun, 2004-07-25 at 20:33, Andrew Piskorski wrote:
> I remember folks on this list suggesting that plugging a high-speed
> interconnect into the memory slots on a standard PC motherboard might
> be a good design.  Well, seems that some Japanese researchers built a
> prototype of exactly that, two years ago - 8 Gbps full-duplex, latency
> around 100 ns:
> "Low Latency Communication on DIMMnet-1 Network Interface Plugged into
> a DIMM Slot"  http://portal.acm.org/citation.cfm?id=825996
> Seems interesting.  Anyone know more?  Has anyone commercialized it?

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