That is really strange. I run Firefox on two different machines (plus my phone). One is my PC which is several years old and the other is my work's Mac which is

That is really strange. I run Firefox on two different machines (plus my phone). One is my PC which is several years old and the other is my work's Mac which is also showing its age. Yet Firefox runs pretty fast on both (while other apps struggle, especially on my work Mac). I rarely see that yellow bar during typical usage...