If you want to run ETHOS and mine on 4gb cards its simple.
Load miner-manager for ethos....
https://github.com/cynixx3/third-party-miner-installer-for-ethosThen once installed simple do a miner-manager phoenixminer install
and it will mine on 4gb cards no issue AMD or nvidia.
My rigs are all up and mining away no issue. Even have claymore V15.0 running with 6/8 gb cards....no issue.
Most likely you were running the default etherminer.
In fact just posted in PM thread here screen shows of my 4gb amd cards 570s still hitting 31mhs this morning no issue.