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
Read more about this topic: Intel 80486
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