The Intel 80386

Dan Knight - September 2001

The 80386 initially shipped at 16 MHz in October 1985, making it faster than any Intel version of the 80286. Although the 386 included the same addressing modes as the 8086 and 80286, it also included new addressing modes, including one that emulated multiple 8086 processors and another that worked within a linear memory space. This architecture forms the foundation of all x86 processors since 1985.

The '386, later known as the 386 DX, had a 32-bit data bus and was designed using a 1 micron process. It contained 275,000 transistors. The 386 DX was capable of addressing 4 GB of RAM and 64 TB (terabytes) of virtual memory.

Byte magazine (May 1993) noted that the 80386 had a MIPS (million instructions per second) rating of 5 (at 16 MHz) to 11.4 (33 MHz). This is an average of 0.33 MIPS per MHz of clock speed. This indicated the 386 is up to 50% more powerful than the 0.21 MIPS/MHz rating of the 80286, although we must keep in mind that MIPS is not an accurate pedictor of real world CPU performance.

In hopes of killing of the 80286 processor, which several different companies manufactured, Intel devised the 80838 SX, the same basic CPU as the 386 DX, but with a 16-bit address bus. Intel shipped both the DX and SX in 16, 20, 25, and 33 MHz speeds. AMD pushed their Am386 to 40 MHz, where it was fairly competitive with the 20 MHz 486.

Further Reading

• Great Microprocessors of the Past and Present, Intel 8086: IBM's Choice, John Bayko

Low End PC (LEPC) launched September 2001. The entire LEPC site copyright ©2001-2003 by Cobweb Publishing, Inc., unless otherwise noted. Copyright of individual articles resides with the author. All rights reserved.
  Advice presented in good faith, but what works for one may not work for all. Computers are like that. Please report errors to the webmaster.
  Letters sent to LEPC may be published at our discretion. Email addresses will not be published unless specifically requested. If you prefer that your message not be published, clearly mark it "not for publication." Letters may be edited for length, context, and to match house style.
  LINK POLICY: This site allows and encourages links to any public page, so long as the linked page does not appear within a frame that prevents bookmarking the linked page.
  PRIVACY POLICY: In brief, we don't collect any personal information unless you explicitly provide it.
  Low End PC is an independent publication and has not been authorized, sponsored, or otherwise approved by Microsoft, Intel, or anyone else. Many company and product names may be trademarks or registered trademarks of the individual companies and are hereby acknowledged.
  For more details, see our Terms of Use.