Various papers describe the software, although they are hard to find. My earlier blog post goes into some detail: https://www.righto.com/2024/01/intel-386-standard-cells.html

The 386 used a placement program called Timberwolf, developed by a Berkeley grad student and a proprietary routing tool.

Also see "Intel 386 Microprocessor Design and Development Oral History Panel" page 13. https://archive.computerhistory.org/resources/text/Oral_Hist...

"80386 Tapeout: Giving Birth to an Elephant" by Pat Gelsinger, Intel Technology Journal, Fall 1985, discusses how they used an Applicon system for layout and an IBM 3081 running UTS unix for chip assembly, faster than the VAX they used earlier. Timberwolf also ran on the 3081.

"Design And Test of the 80386" (https://doi.org/10.1109/MDT.1987.295165) describes some of the custom software they used, including a proprietary RTL simulator called Microsim, the Mossim switch-level simulator, and the Espresso PLA minimizer.