When I left you in my last post on saving energy in the computer labs, I had four machines suspending in the M210 computer lab. There were mixed results during the test run. The older, Dell Dimension 4600 computers went to sleep and woke back up without a problem, however the newer Dell Optiplex 745 computers failed to come out of suspend approximately 30% of the time. Try as I might, updating drivers and playing with BIOS and power settings, I was unable to resolve this problem. I’m in communication with Dell, and hope to find out why the machines will not wake up and come to a solution shortly. In the mean time, hibernation works just find the Optiplex 745, at the cost of an additional five seconds in wake up time (a total of ten seconds to come out of hibernation). The difference between sleep (or standby, which is a synonym for sleep in a computer) and hibernation is that when a machine is sleeping, a snapshot of the state the computer was in before sleep is kept in the computers RAM. When hibernating, the state is stored on the hard disk. Since RAM is faster than the hard disk, the machine can wake up much faster from suspend than hibernate. The cost of using suspend is that power has to be supplied to the RAM so that the stored state will not be lost. Hard disks are persistent, and do not require power to keep the stored state. With our computers, the difference in power saving is only a couple of Watts per machine.
With the eventual success of the test run, I have implemented hibernate and suspend programs in all of our windows labs: M210, the Cad Lab, the digital electronics lab (C221) and the analog electronics lab (C222). The newer Optiplex computers are being sent into hibernation, while the older Dimension computers are being sent into suspend. As always, comments and suggestions are welcome.
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