Jed Rothwell wrote:
Robin van Spaandonk wrote:
Somewhat off topic, but see:
http://www.intel.com/research/platform/terascale/teraflops.htm?iid=newstab+supercomputing
I wonder what they charge for it?
It is NFS (Not For Sale). It is just a prototype device. It does not
do any useful computation, but it does useless work at
record-breaking speed. (Which, come to think of it, is how you might
describe Windows.) This one was designed to test the new "mesh"
interconnections between the cores. This interconnection scheme can
be scale up to thousands of cores, apparently.
Physically, a mesh scales arbitrarily, so hardware designers love them.
In terms of software algorithms which use mesh communication, however,
the scaling is horrible. Traffic density at the middle of the mesh goes
up in direct (polynomial) relationship with the number of nodes so you
can't scale very far before the central links are saturated. To break
the bottleneck you need to add "long lines" so distant nodes can
communicate and at that point it's not a simple mesh anymore.
The diameter is also pretty bad compared to fancier architectures. (Of
course, this is the flip side of the link saturation problem, as sending
a message along paths with many hops uses a lot of interconnect resources.)
Adding dimensions to the mesh improves things. Wrapping around the
ends, to turn the mesh into a hypertorus, improves things quite a lot
but it requires connections from opposite sides of the mesh. That's how
BlueGene is architected, by the way.
They are still working
on the memory, which is some secret new configuration. See:
http://www.theinquirer.net/default.aspx?article=37572
They figure it will be available in a practical version in about 5
years.
Japanese researchers last year demonstrated a 512-core math
coprocessor that may achieve 2-PFlops next year. See:
http://www.channelregister.co.uk/2006/11/06/japan_512-core_co-pro/
- Jed
