GNFS has several stages:

1: Searching for small factors with ECM. If you know it doesn't have any small factors you can skip this (RSA numbers usually don't).

2: Searching for a polynomial. This can be aided by your GPU. And split over several systems.

3: Sieving for relations. This can be split over several systems, each core on each system sieving a separate range. Be careful to ensure you don't sieve the same range more than once, this produces duplicate relations which are useless.

4: Building a matrix (by running msieve -nc1). It may fail saying it needs more relations, if so sieve some more. But don't take the message saying how many more it needs seriously. This is single threaded.

5: Solving the matrix (msieve -nc2). This may take several days for RSA170. It can use multiple cores on 1 system.

6: The square root stage (msieve -nc3) which finds the factors. This is single threaded.

You might do better to start by factoring RSA100 first (In a different directory to the one you are working in). That should not take long and seeing it all the way through will tell you what to expect in larger runs.

Then RSA110, RSA120, etc. Each will take about 4 times as long as the last.

Also look at the NFS@Home forum thread

http://mersenneforum.org/showthread....20023&page=162 on linear algebra. You can read the msieve logs for similar sized jobs which might be helpful.

HTH

Chris