I'm still getting low hashrate on my Vega 56 with max settings of core 930 mem clock 900 and 840mv any thing higher than this the GPU will crash in hiveOS, my hashrate is 44mH and here is the tweak settings I use
amdmemtweak --cl 18 --ras 23 --rcdrd 22 --rcdwr 11 --rc 34 --rp 13 --rrds 3 --rrdl 4 --rtp 6 --faw 12 --cwl 7 --wtrs 4 --wtrl 4 --wr 11 --rfc 164 --REF 15000
The memory is hynix memory
44MH/s is not bad. For anything higher you need to raise core clock to 1000MHz or more and mem clock.
Hynix is not good for overclocking on vega56 cards. If you can flash vega64 bios do it and raise mem clock to 950-1000MHz.
Try to lower --rcdrd as much as you can.
This is a basic settings for hynix memory: --RAS 24
--RCDRD 19 --RCDWR 4 --RC 35 --RP 13 --RRDS 4 --RRDL 5 --RFC 148 --REF 15600