On Tue, Feb 13, 2007 at 11:14:55AM +0100, Vincent Diepeveen wrote: > Can you explain the OS issue to us?
DRAM die piggy-backing is rather expensive and has its own limit on the memory bandwidth issue, so long-term memory will have to be embedded within the CPU. Because of yield limits such embedded RAM will have only very small sizes, few MBytes at best. (This also opens the way to wafer-scale integration, which has also been overdue for a very long time). Current kernels would be hard-pressed to alone fit into such tight memory spaces. Fortunately, there is no point to include code for e.g. I/O, MMU (notice the Cell doesn't do MMU for SPEs, instead using cache transistors as SRAM), video etc. in an effectively embedded node, so kernels can be slimmed down to few 10 kBytes, thus limiting redundancy. Another critical point is to put message passing (ideally, a subset of MPI) directly into machine instructions, to limit latency. The on-die/on-wafer mesh fabric has to send message with almost the same penalty as the on-die access. OOP does implicit memory protection if there are enough cores, because the only way to impact another node's address space is by sending a message. There also needs to be a machinery which allows a large object to be recursively decomposed into composite objects, which will eventually fit into such a small node. This is not exactly Beowulf anymore, even if such hardware is commodity. Linux might have some life in it, though, if it goes the L4/L3 way, and only runs the whole Linux hog on the fat node (host system). Caveat: my crystal ball might or might not be defective. It's been showing me the same thing for the last decade. -- Eugen* Leitl <a href="http://leitl.org";>leitl</a> http://leitl.org ______________________________________________________________ ICBM: 48.07100, 11.36820 http://www.ativel.com 8B29F6BE: 099D 78BA 2FD3 B014 B08A 7779 75B0 2443 8B29 F6BE _______________________________________________ Beowulf mailing list, Beowulf@beowulf.org To change your subscription (digest mode or unsubscribe) visit http://www.beowulf.org/mailman/listinfo/beowulf
