Intel 80486 - Models

Models

There are several suffixes and variants. (see Table). Other variants include:

  • Intel RapidCAD: a specially packaged Intel 486DX and a dummy floating point unit (FPU) designed as pin-compatible replacements for an Intel 80386 processor and 80387 FPU.
  • i486SL-NM: i486SL based on i486SX
  • i487SX (P23N): i486DX with one extra pin sold as an FPU upgrade to i486SX systems; When the i487SX was installed it completely disabled the existing i486SX on the motherboard, taking over all of its functions.
  • i486 OverDrive (P23T/P4T): i486SX, i486SX2, i486DX2 or i486DX4. Marked as upgrade processors, some models had different pinouts or voltage handling abilities from 'standard' chips of the same speed stepping. Fitted to a coprocessor or "OverDrive" socket on the motherboard, worked the same as the i487SX.

The specified maximum internal clock frequency (on Intel's versions) ranged from 16 to 100 MHz. The 16 MHz i486SX model was used by Dell Computers.

One of the few 486 models specified for a 50 MHz bus (486DX-50) initially had overheating problems and was moved to the 0.8 micrometre fabrication process. However, problems continued when the 486DX-50 was installed in local bus systems due to the high bus speed, making it rather unpopular with mainstream consumers as local bus video was considered a requirement at the time, though it remained popular with users of EISA systems. The 486DX-50 was soon eclipsed by the clock-doubled i486DX2 which instead ran the CPU logic at twice the external bus speed.

More powerful 486 iterations such as the OverDrive and DX4 were less popular (the latter available as an OEM part only), as they came out after Intel had released the next generation P5 Pentium processor family. Certain steppings of the DX4 also officially supported 50 MHz bus operation but was a seldom used feature.

Model Specified max clock Voltage L1-Cache Introduced Notes
i486DX (P4) 20, 25 MHz
33 MHz
50 MHz
5V 8 KB WT April 1989
May 1990
June 1991
The original chip (without any clock doubling)
i486SL 20, 25, 33 MHz 5V or 3.3V 8 KB WT November 1992 Low power version of the i486DX, reduced VCore, SMM (System Management Mode), stop clock, and power saving features – mainly for use in portable computers
i486SX (P23) 16, 20, 25 MHz
33 MHz
5V 8 KB WT September 1991
September 1992
An i486DX with the FPU part disabled or missing. Early variants were parts with disabled (defective) FPUs. Later versions had the FPU removed from the die to reduce area and hence cost.
i486DX2 (P24) 40/20, 50/25 MHz
66/33 MHz
5V 8 KB WT March 1992
August 1992
The internal processor clock runs at twice the clock rate of the external bus clock
i486DX-S (P4S) 33 MHz; 50 MHz 5V or 3.3V 8 KB WT June 1993 SL Enhanced 486DX
i486DX2-S (P24S) 40/20, 50/25 MHz (66/33 MHz) 5V or 3.3V 8 KB WT June 1993
i486SX-S (P23S) 25, 33 MHz 5V or 3.3V 8 KB WT June 1993 SL Enhanced 486SX
i486SX2 50/25, 66/33 MHz 5V 8 KB WT March 1994 i486DX2 with the FPU disabled
IntelDX4 (P24C) 75/25, 100/33 MHz 3.3V 16 KB WT March 1994 Designed to run at triple clock rate (not quadruple as often believed; the DX3, which was meant to run at 2.5x the clock speed, was never released). DX4 models that featured write-back cache were identified by an "&EW" laser etched into their top surface, while the write-through models were identified by "&E".
IntelDX4WB 100/33 MHz 3.3V 16 KB WB October 1994
i486DX2WB (P24D) 50/25, 66/33 MHz 5V 8 KB WB October 1994
i486DX2 (P24LM) 90/30 MHz; 100/33 MHz 2.5-2.9V 8 KB WT 1994
i486GX up to 33 MHz 3.3V 8 KB WT Embedded Ultra-Low power CPU with all features of the i486SX and 16 Bit external data bus. This CPU is for embedded battery-operated and hand-held applications.

WT = Write-Through cache strategy, WB = Write-Back cache strategy

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