IntelDX3
The IntelDX3 was intended to make use of a 2.5× multiplier (used by the Socket3 Pentium Overdrive), using the same die as the IntelDX4. For unknown reasons the IntelDX3 was never released. In the official white papers for the IntelDX4 there are instructions for enabling the 2.5× multiplier, however the feature was not implemented in the production version.
Read more about this topic: Intel DX4