Do your problems all involve finding the maximum of a real-valued function? Do you have too much time and/or money? Then it doesn't take an IBM 5100 to figure out that computers may be just right for you! (memory not included, internet not invented, see store for details)
,400 in today's money and you still need two people to carry it. (Yes, I know one person could carry it but if you drop it you've lost the equivalent of a brand new car.)
I guess what we need to remember here is that computers back then were basically floor units connected to banks of reel to reel magnetic tape drives and programmed with huge punch-card reader machiines. I guess that makes this truly "portable" in that sense.