I'm chatting with an expert on this, but from the messages in your last post it looks like you have IO subsystem contention - not enough IOPS to handle the required load. CheckDB when run Physical_Only is disk-bound (if I recall) and hence is going to be hammering the drives.
Maybe worth checking SAN logs (I assume it's a SAN), see what the throughput is and what errors there are, if any.
Gail Shaw
Microsoft Certified Master: SQL Server, MVP, M.Sc (Comp Sci)
SQL In The Wild: Discussions on DB performance with occasional diversions into recoverability