WPerf is another little performance monitor that presents data a little differently than Windows NT Performance Monitor. Be sure to grab a corner of the window when it comes up, and enlarge the window. Then double click on the window to get to the Select menu. This permits the selection of a variety of counters, including two counting TB fills that are not available in Performance Monitor because they are only relevant to certain RISC machines. The TB is the page translation buffer in the processor, which is used to translate virtual addresses to physical addresses without having to go to memory to do so. On some RISC machines resolving TB misses is a software operation, and its high frequency is a drain on system performance.