The IntelDX4 microprocessor is mostly pin-compatible with the 80486, but requires a lower 3.3-V supply. Normal 80486 and DX2 processors use a 5-V supply; plugging a DX4 into an unmodified socket will destroy the processor. Motherboards lacking support for the 3.3-V CPUs can sometimes make use of them using a voltage regulator (VRM) that fits between the socket and the CPU. The DX4 OverDrive CPUs have VRMs built in.
