Yes, Cas can be set in BIOS on most boards. Setting it too high results in instability. Some RAM can take a small decrease in timing, others can't. Sometimes increasing vDIMM helps.
<font color=blue>Only a place as big as the internet could be home to a hero as big as Crashman!</font color=blue>
<font color=red>Only a place as big as the internet could be home to an ego as large as Crashman's!</font color=red>