The core of TeX is fast enough for any modern hardware, even tablets. For example, my laptop can compile the 494 page TeXbook (http://www.ctan.org/pkg/texbook h

The core of TeX is fast enough for any modern hardware, even tablets. For example, my laptop can compile the 494 page TeXbook (http://www.ctan.org/pkg/texbook http://www.ctan.org/pkg/texbook) in about half a second. What slows TeX down is that many packages use extremely elaborate abstractions, which all need to be evaluated using string expansion. These days you shouldn't be surprised if some package is using floating point emulation with TeX macros (https://github.com/latex3/svn-mirror/blob/master/l3kernel/l3fp.dtx https://github.com/latex3/svn-mirror/blob/master/l3kernel/l3...) behind your back. Handy yes, but certainly not fast.