Hi, I'm not sure but since I don't experience this on any other site I assume it's a bug on Scratch.
After the latest update we started to see massive lag when using effects on sprites and backgrounds.
All the effects, mostly brightness and colour, causes my processors to run at maximum performance.
I'm using:
MacBook Pro 2012 (8GB RAM and Intel Dual Core i7 @2.9Ghz)
Flash version 11.8.800.94 (latest official version at the moment)
Safari version 6.0.5 (latest official version at the moment)

Here's some clear examples:

• In the intro of this: http://scratch.mit.edu/projects/10126059/
• All the time playing this: http://scratch.mit.edu/projects/2989999/
• I especially experience processor over-clocking when using the brightness and colour effects!
I also noticed the more effects you use in combination the more process usage it takes.
I made a demo project for you. Just to make the issue easier to debug:

http://scratch.mit.edu/projects/11715395/

Yllie wrote:

Flash version 11.8.800.94 (latest official version at the moment)

That. That may be the cause of all the lag. Downgrade to Flash 11.7 something or use Firefox.

You are quite right. The only issue I have is your use of the term “over clocking”. Its increasing the cpu usage. Your cpu is just increasing its clockspeed to compensate. So your title should be “Effects causing massive cpu usage”.

ProdigyZeta7 wrote:

Yllie wrote:

Flash version 11.8.800.94 (latest official version at the moment)

That. That may be the cause of all the lag. Downgrade to Flash 11.7 something or use Firefox.

That might actually be the issue since I upgraded to 11.8 around the same period as they updated Scratch. I'll try to downgrade.
Thanks!

drmcw wrote:

You are quite right. The only issue I have is your use of the term “over clocking”. Its increasing the cpu usage. Your cpu is just increasing its clockspeed to compensate. So your title should be “Effects causing massive cpu usage”.

Right, of course. Sorry

I found the issue! It IS the latest version of the flash player that causes the massive cpu usage when using effects. Downgrade to version 11.7 and everything should work perfectly again!

ProdigyZeta7 wrote:

Yllie wrote:

Flash version 11.8.800.94 (latest official version at the moment)

That. That may be the cause of all the lag. Downgrade to Flash 11.7 something or use Firefox.

im getting lag and im on Firefox.

Yllie wrote:

I found the issue! It IS the latest version of the flash player that causes the massive cpu usage when using effects. Downgrade to version 11.7 and everything should work perfectly again!

Still happens on 11.7 for me on Chrome.

Yep, they're all right! Everyone's having problems with the new flash player. Also, your processor is not over-clocking, they are simply running at high performance.