https://bugs.freedesktop.org/show_bug.cgi?id=76490
--- Comment #122 from Franc[e]sco lolisamurai@tfwno.gf --- I also edited this piece of code (still in si_dpm.c) to let my memory clock hit 1400 MHz which is stock speed for this card, and I'm still running rock solid:
/* limit all SI kickers */ if (rdev->family == CHIP_PITCAIRN) { if ((rdev->pdev->revision == 0x81) || (rdev->pdev->device == 0x6810) || (rdev->pdev->device == 0x6811) || (rdev->pdev->device == 0x6816) || (rdev->pdev->device == 0x6817) || (rdev->pdev->device == 0x6806)) max_mclk = 145000; } else if (rdev->family == CHIP_VERDE) { ...
Not sure why it doesn't hit my 1450MHz overclock (which is flashed to the card's bios), but I'm very pleased compared to the previous 1200MHz.