Important: CPUClock is only of use on hardware that is capable of switching the CPU between two speed settings. This means hardware such as the OMAP3 BeagleBoard, the OMAP4 PandaBoard, the iMX6, or the IGEPv5.
The following description uses extracts from a post by Jeffrey Lee in the ROOL forum (with permission).
RISC OS does several things to control the speed of the CPU:
Both CPUClock and CPUTmpMon rely for correct operation on the wimp multitasking and wimp polls occurring. If an application is single tasking then no wimp polling is occurring, and both CPUClock and CPUTmpMon will be suspended. Thus no temperature control will be possible during this time. If there is a danger of the cpu overheating during such a period, then you should reduce the cpu fast speed manually before starting the intensive single tasking process.
For a new installation, simply drag and drop the CPUClock application into the directory of your choice.
If you have a previous copy of CPUClock you have two choices.
CPUTmpMon is located within the CPUClock application so will be installed when CPUClock is installed.
To run the application, double click on it's icon in a filer window. Clicking on the iconbar icon with Select will open the CPU status window.
CPUClock will show the set values for the cpu fast and slow speeds, and will also show the current cpu speed (either the fast or slow speed depending on the cpu loading at the time). The actual cpu speeds used for the fast and slow speeds can be set, using a popup menu.
This version interacts with the application CPUTmpMon to obtain the CPU temperature, allowing automatic reduction in the CPU fast speed if the temperature rises too much. Once the temperature falls, the fast speed is increased again.
Note that there are four different versions of CPUTmpMon supplied within the CPUClock application, since the four boards (BB, PB, iMX6, IGEPv5) have very different hardware and different ways of acquiring the silicon temperature. When CPUClock first starts up, it interrogates the hardware, and runs the version of CPUTmpMon appropriate for that hardware. When using CPUTmpMon in this way, its icon (which shows the cpu temperature) will be placed on the iconbar in addition to the icon belonging to CPUClock.
A screen shot of the iconbar menu is shown
right.
Info – A standard application info box, including a button to go to the web site to check for later versions.
Help... – Runs the help file (this one).
Status... – Opens the CPU clock speed status window (see below). Clicking on the iconbar icon with Select will also open the CPU status window.
Choices... – This opens the application choices window (see below).
CPUTmpMon – This leads to a submenu that allows you to Quit CPUTmpMon if it is running, or conversely to start CPUTmpMon if it is not running.
Quit – This terminates the application immediately.
The choices dialogue has a set of action
buttons at the bottom of the window.
The actions available are:
The remainder of the settings are concerned with how CPUClock interacts with the CPUTmpMon application, and how it controls the CPU speed.
Additionally, if choices have previously been saved with auto temperature control enabled, then CPUClock will start CPUTmpMon automatically when it is itself started.
If the auto speed control is enabled, then the following settings will influence how the control will be actioned
The final option applies when CPUClock is quit.
The CPU clock speed can be set to a 'fast' and a 'slow' speed. The OS can switch between the two speeds depending upon how hard the CPU is working. The three display fields show information on the CPU clock speed. The top field shows the configured setting for the 'fast' speed. The middle field shows the corresponding setting for the 'slow' speed. The bottom field shows the actual clock speed of the cpu when it was last read. This will switch between the 'fast' and 'slow' setting as the work load of the cpu changes. By default the fast and slow settings will be the maximum and minimum speeds at which the cpu can be clocked, although the 'fast' speed may be temporarily reduced when in CPU temperature control mode.
Note that CPUClock updates the current speed value, by default, every 1 second using wimp NULL poll events. See Choices (above). If the wimp is not multitasking at that instant, e.g. processing an image, then the display cannot be updated. However, in general use you should see the speed being switched between 'fast' and 'slow' as you do things in the desktop.
The harder the CPU works, the warmer it will get. It might be useful at certain times of high ambient temperature to limit the speed of the CPU to keep its temperature down.
Clicking on the popup menu button to the right of the 'Fast' or 'Slow' fields will raise a menu listing the allowable CPU clock speeds. Selecting one of these speeds will reset the 'Fast' or 'Slow' setting as appropriate to this new value. This is a 'permanent' setting in the sense that it will remain in force until either specifically changed again, or the machine is rebooted.
Reducing the 'Fast' speed may be beneficial in high ambient temperature conditions. It is unlikely there will be any benefit in raising the 'Slow' speed, since this is used when the processor is idling.
In addition, with this version of CPUClock, the CPU temperature can be continuously monitored using CPUTmpMon, and the CPU speed throttled automatically to keep the temperature within safe limits. See Choices (above) and the next section.
If the status window is maximised, by clicking the icon at the far right of the title bar, more display fields are revealed. A screenshot is shown below.
All communication about CPUClock should be directed to Chris Johnson (Email:chris@chris-johnson.org.uk). Suggestions for new features are always welcome.
Chris Johnson's web site is at http://www.chris-johnson.org.uk/index.html, with his RISC OS software at http://www.chris-johnson.org.uk/software/index.html.
All the screen shots in these pages were obtained using Snapper, a versatile screen capture application.
Snapper is available from http://www.chris-johnson.org.uk/software/snap.html
CPUClock is © Chris Johnson, 2012
Email:chris@chris-johnson.org.uk
This document last modified on 17th December 2015