Intel i486

The Intel i486 is the successor to the i386. It was released in 1989 and was similar to the 386, but the improvements were such that it was twice as fast at a given frequency.

The first 486s were made with a 1 µm process and incorporated 1.2 million transistors. They were first available as 25 MHz parts, and frequencies up to 100 MHz were made available later. AMD also manufactured i486 clones, with frequencies up to 150 MHz in their 5x86 line (some references mention a 160 MHz model but we are not sure if it really exists, the 150 MHz appear extremely rare and 133 ones are commonly found).

Like the 386s, the 486s had several suffixes:

DX: the original, which also includes the floating point unit unlike the 386DX which had the separate 387DX.
SX: a cheaper version without FPU, but still with a 32-bit external bus unlike the 386SX.
DX2: a version clocked at twice the bus frequency (multiplier 2x). There were also SX2 without FPU.
DX4: a version clocked at three times the bus frequency (multiplier 3x).

When not soldered, 486s were installed in Sockets 1, 2, or 3.

There were also OverDrives, which allowed to upgrade a lower mutiplier 486, either by installing it on another socket (ODP486) or by replacing it directly (ODPR486).

Intel A80486-25 — An A80486-25 SX249. Bottom. USA, 1989 Week 41.

An A80486DX-50 SX710. Bottom. 1992 Week 51.

An A80486DX2-50 SX641. Bottom. 1993 Week 13.

An A80486DX4-100 SX900. Bottom. 1994 Week 20.

Intel A80486DX-50 — An A80486-25 SX249. Bottom. USA, 1989 Week 41.

An A80486DX-50 SX710. Bottom. 1992 Week 51.

An A80486DX2-50 SX641. Bottom. 1993 Week 13.

An A80486DX4-100 SX900. Bottom. 1994 Week 20.

Intel A80486SX-33 — An A80486SX-33 SX680. Bottom. 1993 Week 11.

An A80486SX2-50 SX845. Bottom. Malaysia, 1994 Week 27.

An ODP486SX-25 SZ800. Bottom. 1993 Week 27.

Intel A80486SX2-50 — An A80486SX-33 SX680. Bottom. 1993 Week 11.

An A80486SX2-50 SX845. Bottom. Malaysia, 1994 Week 27.

An ODP486SX-25 SZ800. Bottom. 1993 Week 27.

Intel 386 and 486 Keychain — A Keychain with a 386 Die on one side and a 486 Die on the other.

A 6" Silicon Wafer of Intel 80486DX4 Chips. More Views: 1b, 2, 3a, 3b, 3c, 4a.

The i486 is suceeded by the original Pentium in 1993.

Intel i487SX Coprocessor

The Intel i487SX coprocessor was released in 1991 and could be paired with an i486SX in order to provide its missing FPU. It was actually a fully working and modified 486DX that took over the 486SX when installed. Some motherboards are even able to use a 487 as a normal 486DX!

Intel A80487SX — An A80487DX SZ494. Bottom. USA, 1991 Week 25.

Operating System Support

Windows 95 officially requires a 486 in order to work thought it can actually run on a 386. Windows Me and 2000 officially require a Pentium, but can actually work on a 486 and be forced to be installed on such machine by disabling a check. Windows XP complains about the missing CPUID and CMPXCHG8B instructions, and we are not aware of anyone being able to run XP on a 486. It can however run on a 486 platform with a Pentium OverDrive.
There were discussions in 2022 about dropping i486 support by the Linux Kernel, but we have yet to see any news of this actually becoming effective. That being said, Linux Distributions generally dropped support long ago.

Debian dropped support for 486s in 2011 with its Version 6.