Yes, v3.87 introduced a new method for measuring CPU clock speed. This method should be more accurate for systems with Nehalem and Sandy Bridge CPUs.
The 12x multiplier which you see might be the EIST triggered LFM clock when there's no load on CPU. So are you sure your CPU doesn't lower the clock when idle?
AFAIK, CPU-Z doesn't refresh the clock as frequent as HWiNFO does, so that might be the reason why you don't see the 12x fluctuations there.
Please answer the following questions:
1. What CPU do you have and what Operating Points are reported by HWiNFO. Is 25-26 the Turbo Mode ratio?
1. How have you set the multiplier to constant 25-26 ?
2. Do you have SpeedStep enabled ? If yes, can you try to disable it ?
Also, you can still switch to the previous method used when you disable the "From Bus Clock" option in settings.
Anyway, I still think this new method should be more accurate and able to better reflect idle situations, because the previous one could itself trigger Turbo Boost when the CPU was set to high performance (Energy Performance Bias / Turbo Boost Technology engagement policy set to engage quickly). That means, measuring of CPU clock using the previous method results in putting some load on the particular core and when the CPU was set to such sensitivity, the measuring method would report a higher clock (up-to Turbo mode). Thus the previous measuring method influenced the measured system which has now been reduced to absolute minimum using the new method (From Bus Clock).