Older parts could be damaged somewhat easily by putting multiple drivers onto an internal tristate bus. If one driver is high and another is low, a current flow

Older parts could be damaged somewhat easily by putting multiple drivers onto an internal tristate bus. If one driver is high and another is low, a current flows and one of the drivers is damaged. Newer parts (Spartan-3 and later, maybe even earlier) dropped that feature -- it's no longer possible to create internal bus contention. You can still cause issues by driving an external pin that conflicts with an external driver, but that's pretty standard; even microcontrollers have that issue.