In order to meet the demand for higher and higher clock speeds, Intel created several versions of the 486DX chip.
The original 486DX CPU had the same internal clock speed and the same external clock speed. The DX2 ran an internal clock speed twice as fast as its external clock speed. The DX4 ran an internal clock speed three times as fast as its external clock speed.
The 486 DX2/4 technology allowed PC manufacturers to put faster 486 CPUs on their existing motherboards. This produced a faster PC without increasing motherboard production costs for the manufacturer.