Factorization of Fermat numbers with ECM ======================================== I am assuming that you are on computers running some sort of Windows operating system, but if not, feel free to ask questions. 1) Go to www.mersenne.org and download the newest version of Prime95. This version offers improvements for all the new architectures. 2) After extracting the files, when Prime95 starts to run, tell it that you are just doing the stress test. Otherwise, it will assume that you want to run test for GIMPS to look for a new Mersenne prime. 3) (Optional, but recommended) Run the stress test for a few hours to make sure that your computers don't have any thermal or memory instabilities that will show up if you start running full time. 4) Before starting testing, go to Options and under CPU, set your memory usage to a larger amount. Refer to ecm_timings.xls for information. 5) In the Advanced Menu, choose "ECM". You will be prompted for the exponent you want. Enter the exponent of your choice. For stage 1 bound, enter the needed value. For stage 2 bound, leave it blank (or 0) and the program will choose 100*B1. For number of curves, insert a value that reflects the time you want to dedicate to the serch. You can always edit the worktodo file later in the Prime95 folder to change the number of curves. Also, check the box that says you want to factor 2^P + 1 (rather than 2^P -1). 6) You should be in business. If you want to work on numbers with some known factors, you will need either lowp.txt or lowm.txt or both. Download them from http://www.fermatsearch.org/lowp.txt 7) If you want to use GMP-ECM to run a more efficient stage 2, let us know and I'm sure that someone can point you to a thread that explains how to set that up. If you have a lot of memory, this may be especially worthwhile. But even if you use only Prime95 to do both stages, you will still be making a valuable contribution to the search. Good luck!