CSC/ECE 506 Fall 2007/wiki1 7 2281

Shared address space

Any changes in the organization of address spaces in the last 10 years? Are the interconnection structures different in new computers now than they were 10 years ago? What is the size and capacity of current SMPs? How have supercomputers evolved since the Cray T3E?

In the parallel computing world, this is the range of Memory addresses accessed / shared by multiple processors. "Shared Memory Multi-Processors" is a class of parallel machines which use Shared Address Space for parallelisation.

Trends in Organisation of address spaces

Pentium can access about 4GB of physical Memory and about 64TB of virtual Memory Physical access has now become virtual access, where the user will feel that the memory to be accessed is infinite,

Since Virtual Memory mechanism includes the lower elements in the memory hierarchy for expanding memory addresses. Paging and Segmentation have also evolved to give better access to the Address space. Segmentation being older than Paging; Degmentation had limits, which were overcome by paging (4kb chunks)

Interconnection structure

Interconnection structures have changed over the last many years. Bus-type interconnects have replaced the conventional cross-bar switch type interconnects, giving the best of performance and cost.

Current SMPs (Symmetric Multiprocessing)

A Computer system containing 2 or more processors in the same box, with shared memory, but containing just one OS running on them is termed as a Symmetric multiprocessor system. The downtime of such a system is dependent on the weakest link, ie. the single processors; if one processor is down, the whole system is said to be down.

Supercomputer evolution since Cray T3E

Majority of the supercomputers run on some flavour of Unix or Linux. It has been predominantly Linux since 2004 [ref Wikipedia] There are special purpose Supercomputers available to solve specific problems ;Astrophysics computation and codebreaking ; Molecular Dynamics ; Deepblue for the game of chess;

Measure of computational speed has gone up to TFLOPS (Tera Floating Point Operations Per Second) and has been moving towards PFLOPS (Peta Floating Point Operations Per Second)

Clustered supercomputing, where a cluster of MIMD Multiprocessors are connected togethere, with each cluster's processor being a SIMD.

Current supercomputers can go beyond 300 TFLOPS.While Cray was about 4 GFLOPS.

References

Computer User: http://www.computeruser.com/resources/dictionary/definition.html?lookup=7776
Foldoc : http://foldoc.org/index.cgi?symmetric+multiprocessing
Searchdatacenter : http://searchdatacenter.techtarget.com/sDefinition/0,,sid80_gci214218,00.html
Wikipedia / Supercomputers: http://en.wikipedia.org/wiki/Supercomputers