Windows NT 4.0 Performance Monitor running on computer (4) measures performance on computer (3) while the PT application is running. Running PerfMon on computer (4) moves to that computer much of the load that PerfMon itself produces. A major resource-intensive PerfMon task moved from computer (3) is that of writing performance logs to the hard drive. But even when running remotely, PerfMon still affects test results by adding traffic to the network interface card of computer (3) and processor interrupts on computer (3) as PerfMon counters are reported to computer (4).
Although this addition of PerfMon slows the test system, it does so equitably for all test cases, allowing them to be compared with undiminished accuracy. Even counting the added hardware interrupts of PerfMon on the processor of computer (3), hardware interrupts totaled only about 500 per second, keeping well under the goal of about 1000 per second seen as a maximum for accurate results.