Low clock speeds on 3070?

I have two different machines with a 3070 running Kawpow. Neither one is overclocked. According to gminer, one is at 27 mh/s with 1300 core, and the other is only pulling 16 mh/s and 600 core. How to I increase the performance of the second machine? Trying to overclock the core speed +700 causes it to crash. Any suggestions?