15.6+- khz is the time it takes to produce a single line on a NTSC tv, so the apple screen is probably really running at or near ntsc tv specs Also it was very common in the 80's …

Uh, no. Assuming that we use the binary equivalents of the metric prefixes, a gigamember would be the 2^30th member. That would be member 1,073,741,824. What you are thinking of…