A note about CPU utilization... For HP-UX 11.0 <= system < 11.23 the configure script will select the "pstat" CPU utilization mechanism. This mechanism is the familiar HP-UX idle counter mechanism (for all incense and porpoises) and requires calibration. See src/netcpu_pstat.c for all the details. For HP-UX 11.23 >= system, the configure script will select the "pstatnew" CPU utilization mechanism. 11.23 adds cycle counts for user, kernel and interrupt modes to the idle cycle counter. As such, it _should_ be possible to simply take the sum of the four and the fractions and know how much time was spent in each mode. HOWEVER... there is a bug in the accounting for interrupt cycles, where interrupt cycles go missing. SOOO, since there is an accurate way to know what the total number of cycles should have been over the interval, and we know (ass-u-me) that the idle cycle counter is good (since the pstat mechanism has tested that one OK), we will take the ratio of idle to total cycles to compute CPU util. We will still calculate fractions for user, kernel and interrupt, and report them in debug (-d) output, but with a warning for interrupt time. See src/netcpu_pstatnew.c for all the details. Up through HP-UX 11.23 (aka 11iV2) if you enable burst mode, and happen to send sub-MSS requests and/or responses you _cannot_ assume that the packet per second rate on the wire will match the transaction per second rate reported by netperf, even if you set TCP_NODELAY with the test-specific -D option. The HP-UX 11.X TCP stack likely will be generating some immediate 'standalone' ACKnowledgements which may not be generated by other stacks. This has been reported to the HP-UX TCP folks, and an announcement will be made when that issue is resolved.