VirtualAcorn Technical support:
Power Management issues

This article was originally published in RISCWorld Magazine.

Power Management

There has been a long standing issue on a couple of customers laptops. The fans on these machines would run continuously while VirtualAcorn was running, showing that the processor was working full time, even though the VirtualAcorn power management was installed. This is designed to return all unused clock cycles to Windows, or to put it more simply, VirtualAcorn only gets the CPU time/power it actually needs to do whatever it's doing at the time. If you are sitting at a machine typing into a word processor then RISC OS doesn't need much oomph to keep up with you, so you don't need to run the computers processor flat out. Despite trying lots of ideas, nothing seemed to make any difference to the machines and eventually I was out of ideas.

I was then contacted by Phil Spiegelhalter, who had a laptop with exactly the same problem. Not only did he have the problem, but he also had the solution. His Laptop was usually set to "Presentation" mode, so that Windows didn't know what power saving to apply, so didn't apply any! Setting Windows to "Laptop" mode started the VirtualAcorn power management so that machine ran much cooler, for much longer.

So for anyone who has a laptop it might be worth checking the power management settings under Windows. To do this open the Windows control panel and go to the "Power Options" icon and double click on it. This will open the Power Options window, make sure you have Window correctly configured to run as a "Laptop/Portable".

In the example above the Power Scheme is set to "Home/Office Desk", this setting will allow VirtualAcorn power management to work on a desktop PC. For Laptops the correct setting should be chosen. Going back to the two customer machines in both cases the users had re-installed Windows themselves and for some reason the Power Scheme had been set the same as Phil's machine, to "Presentation" mode. Correcting this solved the power management problem for them. This brings me neatly onto my next topic, re-installing Windows.