Portable 32-bit Forth for the 65C816.
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OF816 is a 65C816 Forth implementation heavily inspired by Open Firmware (IEEE 1275-1994).

Note that OF816 as a base interpreter is not itself an Open Firmware implementation. A full Open Firmware requires additional Forth source to be loaded at bootstrap. Work has started on this (see the ofw directory), but there is much to do, and it is not currently supported on any of the hardware ports (though most of them will be able to do so, eventually).


Among its many features are:

  • Mostly platform-independent. OF816 can be ported easily to new systems.
    • Ports currently exist for the following platforms:
    • New ports require the implementation of a handful of routines.
    • Simple instantiation of one or more Forths in a system.
  • 32-bit cells.
  • ROM-able.
    • The core system does not write outside of data space, except to the 65816 direct page and stack.
    • System variables are provisioned at the start of data space when the sytem is initialized.
  • Optional FCode support (less Device Tree and Package functions).
  • ANS Forth
    • Core, most of Core Ext, Exception, Search Order, and Search Order Ext word sets.
    • Smattering of words from other sets.
    • Good conformance test coverage.


The goal of OF816 is to help get 65C816-based projects off the ground in terms of development and testing. With a little effort it can be brought up on a new system and used to play around with new hardware.

OF816 is not designed for speed. While reasonably performant, the primary goal was compatibility with 32-bit Open Firmware's core word set, cell size, and FCode. This allows the possibility of re-using existing Forth source and FCode to develop hardware drivers, and potentially developing OF816 into a full Open Firmware implementation.


In addition to the links above, please see the LICENSE file, docs\, and the directories under platforms\.

OF816 is licensed under a two-clause BSD license.