I don't know about the early versions, but I believe the final version of IE for Mac, though also numbered 5, used an entirely different browser engine from that on Windows. Tasman
A Mac will keep creating virtual memory swap up to some limit (some multiple of the amount of physical RAM — can't quite remember, possibly 5x) and then it will produce a kind of vague dialog box saying "You've run out of application memory" with a list of applications to force quit.
http://jimmy.grew.al/macie5-twentieth-anniversary/