> -----Original Message----- > From: [email protected] [mailto:[email protected]] On > Behalf Of Greg Lindahl > Sent: Tuesday, October 05, 2010 1:35 PM > To: [email protected] > Subject: Re: [Beowulf] Broadcast - not for HPC - or is it? > > On Fri, Sep 24, 2010 at 08:21:55PM +1000, Matt Hurd wrote: > > > This was not designed for HPC but for low-latency trading as it beats > > a switch in terms of speed. Primarily focused on low-latency > > distribution of market data to multiple users as the port to port > > latency is in the range of 5-7 nanoseconds as it is pretty passive > > device with optical foo at the core. No rocket science here, just > > convenient opto-electrical foo. > > If you go read up about the Blue Gene series of machines' networks, > one of them is a "Eureka" network for global broadcasts. It's only a > minor aspect of most scientific computations, though. There was even a > very low cost, low-latency broadcast network out of Purdue called > PAPERS that used the unused parallel port that used to be available in > most servers. It was pretty amazing what they could do for so little > $$, but I don't think they found that many applications.
PAPERS was pretty neat, but these days, there are fewer motherboards with a parallel port, and even fewer with a "well behaved" parallel port suitable for PAPERing.. You'd also have a tough time getting latencies down in the sub microsecond range, since the parallel port is fundamentally intended to talk to a "Centronics" printer interface, with 1 microsecond setup, 5 microsecond strobe, and 1 microsecond hold time, as I recall. (Plenty fast running to that line printer at 400 characters/second, eh?) The EPP and/or ECP found in more modern equipment runs at maybe a megatransfer/second. You're still limited by the equivalent of LS244 and LS374 kinds of speeds and loads. _______________________________________________ Beowulf mailing list, [email protected] sponsored by Penguin Computing To change your subscription (digest mode or unsubscribe) visit http://www.beowulf.org/mailman/listinfo/beowulf
