RAM Doubler not only used compression technology to double the 'working size' of the physical RAM installed in a computer (for which reason it is very useful on a machine like a Classic II or an early PowerBook), but also was engineered to overcome certain of the limitations in the way MacOS handled RAM generally. One of the reasons it did the latter was so that it could do the former – but it also had other tricks up its sleeve in achieving this goal. It wasn't a perfect solution, but it worked on a number of fronts to provide a better solution than Apple did stock, in much the same way that Speed Doubler did in connection with 68k emulation in ppc chips, and multitasking in System 7. Both products came from the same corporate stable, and one of the good things about them is that they work so well together.

Is there documentation on the speed hit taken when using RAM Doubler? Subjectively, I have not noticed any slow-down in the systems in which I have used it, but would be interested if this were demonstrated somewhere.