VCool will cool your Athlon/Duron processor on Via KT133 or KX133(A) (VT8363, VT8361, VT82C691/693A/694 or VT8371 +VT82C686x) chipsets during idle.
The Athlon (or Duron) enters a lower power state only when its system bus is disconnected. However the (VIA-)Northbridge will only disconnect the bus if its "Bus Disconnect Enable" bit is set and the CPU is in STPGNT state. It allows you to enable this bit so your CPU can relax when there"s nothing to do. Setting this bit might not be enough on some systems as the idle loop provided with the OS will not put the CPU into the STPGNT state recognized by the Northbridge. For those cases it includes an internal idle loop that forces the CPU into the STPGNT mode required by the Northbridge to initiate a bus disconnect.