RE: is i7 870 going to work on dell inspiron 580?
As I advised earlier the only processors that have been tested are listed above. You may install the i5 750 as this has been tested. The i5 760 should also ideally work, however, there is negligible performance difference between the two. The only place the 760 wins is the low power consumption.
i5 750 vs i5 760: http://bit.ly/2gMuIhJ