Shawn Ellis wrote:
Also the Schottkey, but I think this is just a low power TTL...

Faster, actually.  Schottkey TTL is standard TTL, except that special
diodes (called, surprisingly enough, Schottkey diodes) are built into
their circuits.  Those diodes keep the internal transistors from going
deeply into saturation.  This in turn helps them run faster.

There are Schottkey TTL and Low Power Schottkey TTL chips.

"Plain" Schottkey TTL is MUCH faster than regular TTL, but it also
consumes much more power.

Low Power Schottkey TTL is slower, but it's still faster than regular
TTL, and uses less power than regular TTL.

Summarizing, ordinary TTL is being phased out.  Use low power Schottky
TTL instead in new designs.  It runs faster and uses less power.
"Plain" Schottkey TTL runs even faster, but it uses gobs of power and
should only be used when you need very high speed, as in 100 MHz and up.