Does the Mac OS always speed up gif animation?

Has anyone else noticed that when a nice, subtle GIF animation effect is achieved for Windows browsers, the Mac rendering looks like Charlie Chaplin after too many cappucinos?

What is the cause of this speed up? Is OS detection and a different GIF for Macintosh the only fix?

I don't have access for testing on a lot of different Mac browsers, but this problem is there on the latest Mac versions of both MSIE and Netscape. A similar problem (the same problem?) seems to affect Javascript timing as well.