Mining difficulty will go up by 22%. What is you plan to do with 741? 
741 seems outdated for me, even thought I am sitting on free socket.
741 seems outdated for me, even thought I am sitting on free socket.You want to share where you get your magic number from?
And anyone sitting on ACTUAL free electricity and not mining is an absolute idiot. If you have free energy, then what is your reason for not using a 741? You're not making back compete profit fast enough...?
Bitcoin difficulty chart https://bitcoinwisdom.com/bitcoin/difficulty
so what's 20 %
it is nothing.
suppose it follows with
https://bitcoinwisdom.com/bitcoin/difficulty
Date Difficulty Change Hash Rate
Sep 06 2017 922,724,699,726 3.89% 6,605,120,681 GH/s
Aug 24 2017 888,171,856,257 -3.80% 6,357,781,793 GH/s
or this
Nov 05 2016 254,620,187,304 0.40% 1,822,642,296 GH/s
Oct 22 2016 253,618,246,641 -1.90% 1,815,470,125 GH/s
Oct 08 2016 258,522,748,405 7.17% 1,850,577,916 GH/s
Sep 25 2016 241,227,200,230 6.82% 1,726,771,560 GH/s
Sep 12 2016 225,832,872,179 2.30% 1,616,574,667 GH/s
Aug 29 2016 220,755,908,330 1.56% 1,580,232,344 GH/s
Aug 15 2016 217,375,482,757 7.67% 1,556,034,316 GH/s
Aug 02 2016 201,893,210,853 -5.43% 1,445,207,896 GH/s
Jul 18 2016 213,492,501,108 0.04% 1,528,238,850 GH/s
Jul 04 2016 213,398,925,331 1.88% 1,527,569,009 GH/s
Jun 21 2016 209,453,158,595 6.83% 1,499,324,110 GH/s
Jun 08 2016 196,061,423,940 -1.63% 1,403,462,340 GH/s
May 24 2016 199,312,067,531 2.60% 1,426,731,353 GH/s
which actually is from
May 12 to Nov 17 which is 6 months just under 2% a jump
lets make the diff 1844 vs 922 and coins at 4000 see what we get.
https://bitcoinwisdom.com/bitcoin/calculator
Date______________Difficulty___Revenue_____ Profit
9-17 9-17 (1 day)...1844 G.......1.38..............1.367
with a pool charging 1% and diff 1844g 2x current diff the gear still makes 1.36 a day
I used
1844g for diff
10 cents a kwatt