Sorry I'm a bit late to the party.
I'm running Octave 3.2.4, so an older version than flameout
Hardware is Dell E6420 laptop (CPU i7-2640M @ 2.8GHz) Win 7 64bit
Code:
octave:2> N = load('N.dat');
octave:3> d = load('d.dat');
octave:4> tic; Ns = sparse(N); toc
Elapsed time is 0.136 seconds.
octave:5> tic; r = Ns \ d; toc
Elapsed time is 0.096 seconds.
octave:6> tic; r = N \ d; toc
Elapsed time is 0.921 seconds.
So solving the sparse matrix is around 230ms and direct solution is around 900ms.