Intel DX4

IntelDX4 is a clock-tripled i486 microprocessor with 16 KB level 1 cache. Intel named it DX4 (rather than DX3) as a consequence of litigation with Advanced Micro Devices over trademarks. The product was officially named IntelDX4, but OEMs continued using the i486 naming convention.

Intel produced IntelDX4s with two clock speed steppings: A 75-MHz version (3× 25 MHz multiplier), and a 100-MHz version (3× 33.3 MHz or 2x 50 MHz). Both chips were released in March 1994. A version of IntelDX4 featuring write-back cache was released in October 1994. The original write-through versions of the chip are marked with a laser-embossed “&E,” while the write-back-enabled versions are marked “&EW.” i486 OverDrive editions of IntelDX4 had locked multipliers, and therefore can only run at 3× the external clock speed. The 100-MHz model of the processor had an iCOMP rating of 435, while the 75-MHz processor had a rating of 319. IntelDX4 was an OEM-only product, but the DX4 Overdrive could be purchased at a retail store.

The IntelDX4 microprocessor is mostly pin-compatible with the i486, but requires a lower 3.3-V supply. Normal i486DX 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 module (VRM) that fits between the socket and the CPU. The i486 DX4 OverDrive CPUs have voltage regulator modules built in.