Parameter variation probing technique

A technique for probing parameter variations in an integrated circuit chip includes providing a group of ring oscillators disposed over the integrated circuit chip, each oscillator producing an output representative of an integrated circuit chip parameter. A controller is provided to selectively enable one of the group of ring oscillators and a multiplexer is provided to output an output of one of the group of ring oscillators enabled by the controller, Each ring oscillator may include a gated inverter, having an enable/disable input, connected to a group of inverters arranged in a ring, the total number of inverters being an odd number. The group of ring oscillators may include a shift register chain consisting of a group of shift registers, an output of each shift register being respectively connected to an enable/disable input of the gated inverter of one of the group of ring oscillators. The multiplexer may include an exclusive-OR gate having inputs respectively connected to an output of each of the group of ring oscillators. An inverter may be disposed between each output of the group of ring oscillators and its' respective input to the multiplexer.