Intel i386
The Intel i386, originally named 80386, is the successor to the 80286. It was released in 1985 according to many sources, though so far we have yet to see any specimen, even prototype, with an actual 1985 Date Code. The i386 is the first 32-bit x86 processor and was a significant evolution of the x86, to the point that even nowadays, the term "i386" is sometimes still used to refer to software working on 32-bit x86 processors.
There are many variants of the i386, both at the chip (DX, SX, EX,...) and packaging (132-pin Ceramic PGA, various plastic QFP) levels. The first 386s were made with a 1.5 µm process and incorporated 275000 transistors. They were first available as 12.5 MHz parts, which are nowdays very difficult to find, and frequencies up to 33 MHz were made available later. AMD also manufactured i386 clones, with frequencies up to 40 MHz.
Some early 16 MHz were known to be bugged when multiplying 32-bit numbers, so Intel retested their processors. Those that worked fine were marked ΣΣ ("Double Sigma"), the bugged ones were marked "16 BIT S/W ONLY", but still sold since 32-bit features were advanced at the time and not commonly used until a while.
- A White Print A80386-12 S40277 (12.5 MHz), before the multiply bug was found. Bottom. All 12 MHz parts are Extremely Rare. USA, 1986 Week 16.
- An Engraved A80386-16 (16 MHz), made just before Intel started marking the processors (No Sigma). Bottom. Malaysia, 1986 Week 47.
- An Engraved A80386-16 marked "16 BIT S/W ONLY"/SX025. Bottom. Malaysia, 1986 Week 50.
- An Engraved A80386-16 marked "ΣΣ". Bottom. Malaysia, 1987 Week 1.
We are fond of Early 80386s so we have additional ones in our collection: another A80386-12 but with the S40343 Sspec (Bottom), and older A80386-16s with the same appearance as the 12: an S40337 (Bottom) and another S40344 (Bottom): these are common as Engraved but very rare as White Print. We are looking for the rare combination of a White Print that is marked ΣΣ!
Below are more recent ones. 386s were produced until 2007 despite their obsolescence, for example to integrate embedded systems.
- An Engraved A80386-20 S40362. Bottom. Malaysia, 1987 Week 49.
- A A80386DX-16 with the i386 Logo (i386DX 16 MHz, DX being simply the renamed original to prevent confusing with SX and others), well after the multiply bug. Bottom. Malaysia, 1991 Week 7.
- A late White Print A80386DX33 (i386DX 33 MHz). Bottom. Malaysia, 2000 Week 29.
- A PQFP NG80386SX-16 (i386SX 16 MHz). Bottom. 1991 Week 17.
- A PQFP KU80386EX25 (i386EX 25 MHz). Bottom. 2002 Week 5.
- A Keychain with a 386 Die on one side and a 387 Die on the other.
- A 6" Silicon Wafer of Intel 80386EX Chips. Back, 80386EX Microscopic Inscription.
The i386 is suceeded by the i486 in 1989.
Intel i387 Coprocessors
The Intel 387 coprocessor could be paired with a 386 in order to accelerate applications doing intensive floating point calculations. There were also versions like DX and SX for the 386DX and 386SX respectively.
Operating System Support
- Windows 95 officially requires a 386 in order to work. Windows 98 officially requires a 486, but can actually work on a 386 and be forced to be installed on such machine by disabling a check. We are not aware of any Windows Me running on a 386.
- The Linux Kernel dropped support for 386s in 2012 with its 3.8 version, though Linux Distributions generally dropped support well before.
- Debian already dropped support for 386s in 2005 with its 3.1 Version, the missing CMPXCHG instruction introduced in the i486 is cited.
More about the Intel i386
- PCjs: Intel 80386 CPU Information - technical information about 386s, notably some about Early ones.
- Ken Shirriff's blog: Examining the silicon dies of the Intel 386 processor
- Wikipedia: Intel i386.