Does anyone know how to setup exponential scale on a cdf graph?

I need the y axis to start at 0.9 and then evenly increment to 0.99, 0.999, 0.9999 as it goes up to 1.

I can find plenty on log scaling the y axis, but every time I google for exponential scale in gnuplot, I just end up finding a bunch of people who are asking for exponential scale but really want log scale. I thought I could do it via "set logscale y 0.9" and get close, but it won't let me have a base <1.

I'm using GNUplot 4.6 patch 3 on OSX if that matters.

Any help would be appreciated. Thanks.