I have already written BK-G 28 STM-FW to BK-X which Groestl has made it possible to mine.
It was successfully mined by Groestl.
Next, I will try to replace all IMGs and check if it works with BK-X
tested.
cod3gen sgminer + BK-G28 STM-FW = OK (No change hash rate. Groestl about 7GH/s)
BK-G28 IMG to BK-X = NG (No Device running)