Was the sp_sysmon session run while the cpu utilization was high? If not, the sp_sysmon data is useless for troubleshooting this issue. [I ask because your sp_sysmon report is only showing an average of ~15 cpu+io utilization across 64 engines ... nowhere near 100% cpu utilization, eh.]
In the past I've seen some high cpu issues with ASE 12.5.x dataservers with 20+ dataserver engines (you are running ASE 12.5.4 w/ 64 engines). In a couple cases the high cpu utilization was due to a bug with the MDA configuration setting 'object lockwait timing'; in those cases disabling 'object lockwait timing' (ie, set to '0') eliminated the spikes in high cpu utilization.
If disabling 'object lockwait timing' does not address your issue then you'll need to capture more information *WHILE* the dataserver is running at 100% cpu utilization (eg, sp_sysmon, contents of master..monProcessSQLText, snapshots of master..monProcessWaits, etc).
