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CpuIdle was the first of the software cooler programs I was introduced to in mid 1997.  Applying the HLT instructions found in enterprise operating systems to the  Windows OS was sheer brilliance.  From the first time I tried the program and observed the results, I have had one version or another of CPUIdle or another running on at least one of my computers.  With a new version of CpuIdle seemingly always in the works, you never have to wait too long for a new version to arrive.

CpuIdle 5.1
This version of CpuIdle, like version 5.0, has done away with the VxD in the "Windows mode."  The VxD is still used in the "control panel" mode.  The CpuIdle.exe file in the first version of 5.0 was dated September 16,1998 and the updated version (5.0a) had a date of September 19, 1998.  The most recent version, 5.1 has the exe file dated November 5th 1998.  The VxD for all three versions is the same as in the version 4.X, with a date of May 30, 1998.

In the "Windows mode," CpuIdle performs well in controlling temperature rise during file transfers and is on equal footing with Rain and Waterfall Pro.  In "control panel mode," CpuIdle still suffers from less than spectacular performance in keeping the processor cool during file transfers.

A nice addition to the 5.X versions is the display of "Idle Time" since the program began running.  It's interesting to see how much time the processor spends in "Idle" mode. (My CPU spends a lot of time doing nothing!)

Version 5.1 also adds a display for the system's physical memory. 

Another nice feature is that CpuIdle now works in conjunction with Motherboard Monitor to allow you to observe the temperatures read by your motherboards LM75 or LM78 / LM79 chips.  Motherboard Monitor is a nice program and the two programs work well together, though Motherboard Monitor uses a fair amount of memory.

Early in testing, I had a problem with the combination of CpuIdle 5.0 and Motherboard Monitor version 371.  Though it was partially my fault, enabling the LM75 CPU temp sensor when I should have chosen the LM78, I was rewarded with a crash and spontaneous reboot.  While I originally attributed the crash to CpuIdle, I have since discovered that the problem lay with Motherboard Monitor.  This situation was rectified with version 372 and I have had no problems with either CpuIdle or Motherboard Monitor since then.  As of this review, the most recent version of Motherboard Monitor is version 373.

And speaking of monitoring, since the Windows System Monitor is of no use when running any of the CPU cooler programs, due to the fact that the programs start running as soon as the System Monitor would show no activity,  CPUIdle thoughtfully included a CPU use monitor in the tray icon's pop up window.  Comparing the numbers between CPUIdle's monitor and windows' own monitor, they seem to be right in synch.  Good show.

CpuIdle is Shareware with a free 30 day trial and a $20 registration fee if you choose to keep it.  Money well spent.

CpuIdle 5.1 User Interface 

To see how the Cooler Programs compare with each other, check out the Current Tests.

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