I proceed like this, I don't know if it's okay but I can have quite stable results.

Example with one Sapphire Rx570 Nitro 4 gb Hynix, vga bios coming with 2 different chip strap, Elpida and Hynix but my card is equipped only with Hynix H5GC4H24AJ.

I tested a lot of strap but memory limit without error is in range 2045 - 2050 mhz, acceptable mem error until 2070 mhz more than 2070 i can not go without thousand of error.

Overclock and undervolt from Phoenix Miner or with OverdriveNT with the same result.

Ref parameter is set to 30.

1100 - 2050  [900 - 900]  30.65    86w
1110 - 2050  [900 - 900]  30.7      86w
1120 - 2050  [900 - 900]  30.8      86w
1130 - 2050  [900 - 900]  30.95    86w
1140 - 2050  [900 - 900]  31.3      86w
1150 - 2050  [925 - 900]  31.55    90w
1160 - 2050  [925 - 900]  31.6      92w
1170 - 2050  [925 - 900]  31.65    92w
1180 - 2050  [925 - 900]  31.65    92w

Clock > 1160 with ref 30 dont give me more hs so i set to 1150 - 2050 [ 925 - 900 ] for ~ 90w and go stable for days without error.

I can go down with core to ~915mv but after some time go to 0 h/s and restart.

Some question:

• for cvddc i made test with increase of 10mv each step, but effective cvddc in hwinfo is always a few mv less, exist a precise way to increase or decrease the core voltage? 6 mv step or 8 mv step or other?
• plus or minus mv to memory affect memory error?