Maybe with a stronger motherboard you could gain some +200-300MHz stable....I was able to get 4.0/2.8 stable with my 1090T and ASUS M4A79 but needed high voltage in both CPU & CPU/NB.

When i got the CHVF-Z i managed run stable 4.2/3.0 with lower voltages....LLC helped much but also the strong VRM and many bios options..i was even able to run Cinebench @ 4.4/3.0, which was not even a dream with previous motherboard