> I have found two xx164's and two xx595's
>
> is the 595 different, or the main difference that it can be
> powered on and off, or however you might put it, set a bit
> pattern, then turn it all off the turn it back on with this same
> pattern???

The 164 is a plain and simple shift register. The 595 (and
4094) are shift registers + latches that can be tri-stated
through an Output Enable pin. This makes them useful for
buss applications

Philips have an extensive library of information here

http://www.philipslogic.com/datasheets/

and at the sitemap, you can look up specs for products and
protocols for such things as I2C (a Philips system)

http://www.semiconductors.philips.com/sitemap/

This page here will help you decide which 74 series to
choose for a given application. It gives the history of 74 logic
and explains the inner workings of the different families

http://design.stanford.edu/spdl/logic/which_is_best.html

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