Intel Inboard 386

Intel Inboard 386/AT and Intel Inboard 386/PC were 1980s ISA boards which allowed to upgrade respectively an IBM AT or an IBM PC computer into Intel 80386 machines.
The board was a full-length ISA expansion card that came with a 386 processor (16 MHz), an 80387 math coprocessor socket and 1 MB of RAM. 2 MB and 4 MB memory expansion options were also available. The board was activated after the regular XT/AT BIOS had finished its POST (power-on self test) routines and the OS had loaded the Intel DOS-based .sys device drivers (from config.sys).
Disadvantages.
Some of the disadvantages of the product were:
Advantages.
Other than that, one could actually run applications that just would not run on an XT. Some of the applications included: Ventura 2.0 Desktop Publishing Software (with Hercules monochrome graphics), Autocad 386, Windows 3.1 (Inboard 386/AT model only).
External links.
How to 386 Your AT: Intel Inboard 386/AT