got an XFX RX-480P836BM 8GB currently in the 622-623h/s range. did not mod GPU.

[13:10:31] Thread 0, GPU ID 0, GPU Type: Ellesmere: 622.99H/s
[13:10:34] Thread 0, GPU ID 0, GPU Type: Ellesmere: 622.89H/s
[13:10:37] Thread 2, (CPU): 53.54H/s
[13:10:37] Share accepted: 6/6 (100.00%)
[13:10:37] Total Hashrate: 1034.17H/s

in hibernate mode, its even faster

[13:37:07] Thread 0, GPU ID 0, GPU Type: Ellesmere: 626.81H/s
[13:37:10] Thread 0, GPU ID 0, GPU Type: Ellesmere: 626.83H/s
[13:37:10] Share accepted: 17/17 (100.00%)
[13:37:10] Total Hashrate: 1050.57H/s


OS - running xubuntu 16.04LTS with linux amdgpu driver
**both CPU multiplier (20--->21) and bus speed (200--->210) increased in mobo bios.

xmr.conf GPU settings:

"index": 0,
"corefreq": 1275,
"memfreq": 2133,
"fanspeed": 65,
"powertune": 20,
"threads": 1,
"rawintensity": 1022,
"worksize": 8

hope this helps