Ok sounds good. I searched for any replay that mentioned "bench" or "benchmark" but ended up picking a random replay that I actually played in.
So I then walked through the replay and found a 2-minute section that had a good mix of big 3v3 battle and then just the player scrolling around managing his bases. So there is a good fluctuation of FPS indicated by FRAPS. I then set FRAPS to record 120 seconds, and just play the replay and hit the hotkey for FRAPS to start recording at minute 34:00. It automatically stops at 36:00.
It's nice that FRAPS has three checkboxes, to record 1) FPS over time, 2) duration in ms for each frame, and 3) min/max/average. So you don't even have to calculate anything, you just check those three boxes and when you hit the record button in FRAPS, it will save three different reports for you with all that info.
I'll run a few times on the old CPU and then again on the new one. I adjusted the Starcraft settings to set all the CPU-dependent effects to maximum, but I dropped the resolution (from 1920x1080 down to 1600x900) and set all the CPU effects to low. My current CPU has no business running Starcraft with maxed CPU settings, it's quite poor. But maybe it just makes the replacement look even better?