HOWTO discriminate switches?

Patrick Geoffray patrick at
Mon Sep 17 09:06:39 PDT 2001

Hi Richard,

On Mon, 17 Sep 2001, Richard Walsh wrote:
> > Another alternative which starts to make sense as the switching cost
> > of your system rises as a percentage of total cost is a switchless
> > system in the form of a 1D or 2D torus using SCI cards which have
> > extremely low latency and high bandwdth. Take a look at the cluster
> > at the University of Delaware based on this design. If you do the
> > math, I think you will find that for larger clusters which would
> > require multiple layers of switches or a "mega-switch" to build
> > in reasonable bandwidth, the SCI torus design is no more costly and

80 nodes would fit easily on only one Myrinet switch, based on a 
128 ports enclosure and 10 line cards (with place to expand to 128 
ports by adding line cards). This solution provides full
bandwidth bissection at 2 Gb/s full-duplex (Clos topology). 
Hard to do it with a Torus design.

Large switched cluster are no a problem if you know how to build
inexpensive large switch. The real math is that it cost the same 
thing that a switchless topology like SCI. 
FYI, the total price of the interconnect would be $140K with Myrinet,
including NIC, switch, cables and software (public price from the web).

> > are equal to or better than some custom engineered networks from
> > vendors of SMP and MPP systems (Cray, Sun, SGI).

What are these "custom engineered networks" ?



|   Patrick Geoffray, Ph.D.    patrick at         |
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