Hello,
I noticed that on Asus Rampage IV Extreme, AIDA64 sometimes outputs "Thread creation error: Insufficient memory for this operation" and after that readings of OPT1, OPT3, Case 2 and PCH fans become 0.0 RPM (I have OPT2, Case 1 and Case 2 fans unconnected so cannot say anything about them). CPU fan and CPU OPT fan readings are still OK.
If I relaunch AIDA64 (File - Exit - Run again), readings become OK, and sometimes later the problem repeats.
I have to confess that I have ASUS Suite II installed (because and only because AIDA64 missed OPTx temp support on Asus R4E!). After installati