Depending on what the tabs are doing, you can budget 100-300MB/tab, so 100 tabs may require in the neighborhood of 32GB of RAM.
CPU-wise, static content may be fine on a Pentium or Athlon 200GE. If you are running VRML, jscript miner or other stuff that will keep the CPU busy all of the time in every tab, then you may need a ThreadRipper.