Centos 6/7 boot issues on HP DL980

[teemuch]

Having issues booting an HP DL980 server using Centos 6.7+ or 7.x

It will not boot at all using Centos 7.x media - this media works fine on other servers.
We can boot using Centos 6.7 install media, however when we do a yum update, it will no longer boot.

No error messages are given, after reboot it just goes back to bios.

Any ideas on why this is or how to resolve (other than just sticking with 6.7)?