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Old 2015-03-07, 09:29   #5
bloodIce
 
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Feb 2010
Sweden

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I am also interested in the 2M range, but sometimes I go 1M, <1M and rarely 3M. It is only for fun, so don't take my opinion seriously. But, lets talk about 2M. I have 10x less powerful card ( ~29GHd/d) and less efficient than yours (in the tables at www.mersenne.ca it says that mine is 1.005 GHd/W and yours is 1.498 GHd/W). Even with these numbers I usually go in 2M to TF68, before I succumb to Pminus1 or ECM2. Here a powerful enough reason is, that it is not fun any more to go TF70 (or not as effective in finding factors). Usually for the same time I will complete ~250 ECM curves at (B1=5e4 B2=5e6) at the CPU. That way I would test the exponent to ~TF75. The reason I do crazy Pminus1 (or it was crazy with my previous CPU, now seems like fine), after ECM is only for full exhaustion of all viable options in reasonable time. Rarely Pminus1 is of any help after ECM, but sometimes there are surprises. So seeing your GPU, I would say go to TF68 in >2M, clearly at least 1 bitlevel up (TF66). For 1M, I guess TF66 would be fine. Than go ECM, it is still more efficient in finding factors up to 3.5M range. For the rest of you, who would say that I am an idiot, please read my reason again - JFF.
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