YASSC: O CALHAU

YASSC means Yet Another Stone SouperComputer...

Sopa de pedra (stone soup) is a real Portuguese soup, but with a rather vague recipe. All is allowed, the only common ingredient seems to be garlic. So, instead of making a soupercomputer from old PCs we'll make a more spicy one with AMD XPs at 1.5 GHz and 512MB DDR in all nodes. Yum yum.

Sept 2003: the hub is replaced by a switch with 8 100 Mbs ports and one gigabit uplink to the frontend.

As you might have guessed, Calhau means stone/pebble

Test results

On April 23 the 8 nodes achieved a peak of 5.8 GFLOPS.
HdB's test program with 588 2D FFTs took 6.6 seconds, see benchmarking.
On May 8 the first production run: a program that needs 2.5 hours on
the SGI Origin (using 1 R10K CPU) needed 5.6 minutes on the Calhau.
After a few code modifications, this was reduced to 2.5 minutes

Explanation of the difference between 2.5 hours and 2.5 minutes:
MIPS R10000 is RISC with single-cycle adders and multiplyers, but at 180 MHz.
The difference between the runtimes is a factor 60.
60/8 = 7.5 (we use 8 XPs).
7.5x180 MHz = 1.35 GHz ("effective XP clock speed").
This means that the program, including communications and serial processing, can use 1.35 of the 1.5 GHz of the AMD XP (90%).