The IntelDX4 is a clock-tripled i486 microprocessor with 16 KiB L1 cache. Intel named it DX4 (rather than DX3) as a consequence of litigation with AMD over trademarks. The product was officially named the 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 (usually 3× 33.3 MHz, but sometimes also 2× 50MHz). Both chips were released on March 1994. A version of the 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 the 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, whilst the 75 MHz processor had a rating of 319. The 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 80486, but requires a lower 3.3V supply. Normal 80486 and DX2 processors use a 5V supply; plugging a DX4 into an unmodified socket will destroy it. Motherboards lacking support for the 3.3V CPUs can sometimes make use of them using a voltage regulator (VRM) that fits between the socket and the CPU.
The 486DX4 is still in production for industrial applications requiring moderate embedded processing capability.
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.
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