Any information to do it without windoz' ?

6x vega56 on linux, running ethminer w/ Mesa Clover OCL. You can get 39-41mh/s depending on your memclock. Those 6 I have from 1043 to 1083 right now, just testing accept/stale rates to make sure I'm not missing out by running up the clocks. Total TDP is ~1150. You can see the hash rates based on memclocks below.
# clocks
3: 1083Mhz *
7: 1107Mhz *
3: 1083Mhz *
7: 1107Mhz *
3: 1063Mhz *
7: 1107Mhz *
3: 1063Mhz *
7: 1107Mhz *
3: 1043Mhz *
7: 1107Mhz *
3: 1043Mhz *
7: 1107Mhz *
# rates
GPU #0
-----------------------------------------------------------------------------------------
m 12:43:51|ethminer| Speed 40.37 Mh/s gpu/0 40.37 [A590+6:R0+0:F0] Time: 20:59
-----------------------------------------------------------------------------------------
GPU #1
-----------------------------------------------------------------------------------------
m 12:43:56|ethminer| Speed 40.29 Mh/s gpu/0 40.29 [A74+1:R0+0:F0] Time: 02:52
-----------------------------------------------------------------------------------------
GPU #2
-----------------------------------------------------------------------------------------
m 12:43:55|ethminer| Speed 40.04 Mh/s gpu/0 40.04 [A598+5:R0+0:F0] Time: 20:59
-----------------------------------------------------------------------------------------
GPU #3
-----------------------------------------------------------------------------------------
m 12:43:53|ethminer| Speed 40.04 Mh/s gpu/0 40.04 [A570+4:R0+0:F0] Time: 21:01
-----------------------------------------------------------------------------------------
GPU #4
-----------------------------------------------------------------------------------------
m 12:43:56|ethminer| Speed 38.80 Mh/s gpu/0 38.80 [A562+5:R0+0:F0] Time: 21:01
-----------------------------------------------------------------------------------------
GPU #5
-----------------------------------------------------------------------------------------
m 12:43:53|ethminer| Speed 39.15 Mh/s gpu/0 39.15 [A88+1:R0+0:F0] Time: 02:51
-----------------------------------------------------------------------------------------
and wattage @ 875mv cores...
# gfx
GFX Clocks and Power:
1083 MHz (MCLK)
1107 MHz (SCLK)
1138 MHz (PSTATE_SCLK)
800 MHz (PSTATE_MCLK)
875 mV (VDDGFX)
132.0 W (average GPU)
--
GFX Clocks and Power:
1083 MHz (MCLK)
1107 MHz (SCLK)
1138 MHz (PSTATE_SCLK)
800 MHz (PSTATE_MCLK)
875 mV (VDDGFX)
131.0 W (average GPU)
--
GFX Clocks and Power:
1063 MHz (MCLK)
1107 MHz (SCLK)
1138 MHz (PSTATE_SCLK)
800 MHz (PSTATE_MCLK)
875 mV (VDDGFX)
135.0 W (average GPU)
--
GFX Clocks and Power:
1063 MHz (MCLK)
1107 MHz (SCLK)
1138 MHz (PSTATE_SCLK)
800 MHz (PSTATE_MCLK)
875 mV (VDDGFX)
139.0 W (average GPU)
--
GFX Clocks and Power:
1043 MHz (MCLK)
1107 MHz (SCLK)
1138 MHz (PSTATE_SCLK)
800 MHz (PSTATE_MCLK)
875 mV (VDDGFX)
125.0 W (average GPU)
--
GFX Clocks and Power:
1043 MHz (MCLK)
1107 MHz (SCLK)
1138 MHz (PSTATE_SCLK)
800 MHz (PSTATE_MCLK)
875 mV (VDDGFX)
125.0 W (average GPU)
Running nightly kernel, mesa 18, ethminer 0.15.0-dev, etc etc etc...