Hi there,
does anybody know how many CPU load should be a “home made screensaver” ?
I can see that default screensaver are really low energy, almost flat.
I tested my screensaver and it goes up and down. When it goes up is around 25-30% of CPU.
Is it too much?
I ask because my client had a screensaver before and some machines got the CPU overheat…
I would never be responsible for that 
Many thanks
Matteo
Matteo – very good question. It’s possible to make a screensaver which is a CPU “hog” and eats too much. This not only causes computers to run hot, but can waste electricity. We offer general energy-saving tips here:
http://iscreensaver.com/green/
To your question:
Mac and Windows report CPU usage differently. On mac “50%” would be 50% of one core of the CPU. (So if you have 2 cores, this means only 25% usage, etc.) On windows, 50% is the total across all cores (so, on a 2-CPU system, 50% would mean one core was at 100%)
My personal rule of thumb is to try to keep CPU usage around 25%-30% maximum of the total CPUs. Usually it seems that around 30% won’t cause the CPU to heat up, so the fans won’t run loudly, and it leaves enough CPU left over for other tasks (file serving, virus scanning, etc.)
Ways to reduce CPU usage:
for images: use smaller images, allow more time between images (15 seconds instead of 2 seconds)
for SWF: use a smaller stage. play “Actual Size” instead of stretching to fit the screen. Reduce the frame rate (60 and 30 are usually too high, try 24 or 15fps). Reduce the complexity of layered (transparent) animations.
For Movies (Quicktime/H264) : reduce movie size, reduce frame rate, play Actual Size.
Not all computers are alike, so consider making two versions: a “High resolution” version for powerful computers, and a “Low resolution” version for older/slower computers. Generally, Images (OpenGL) will cause the lowest CPU usage. SWF (Flash) and movies will take more CPU.
Many thanks for the suggestions.
I’ll keep it in mind.
Matteo
