README.md

RemoveFloatingPoint - Build an Oberon system without Floating Point support

Description

While floating point is certainly important in general-purpose computers, it is mostly unneccessary in some embedded systems. Also, floating point support needs considerable space on a FPGA, therefore you may want to remove it.

Turns out, there are only very few modules in the Project Oberon outer core that actually require floating point - Files.Mod to read and write REAL values, Texts.Mod to read and parse them, and of course the compiler.

But even when you remove floating point from the compiler, it is straightforward to later compile a compiler with floating point support on the compiler that does not have it (probably because that is the way how floating point support was added to the compiler in the first place).

Splines.patch can be used to compile DrawAddons modification on a system without floating point; expect some rough approximations and overflow artifacts when drawing Splines, though.

Alternatively, SimpleSoftFloat.patch comes with a very crude software floating point emulation (providing only about 4 significant digits on division) and patches both Splines.Mod and RealCalc.Mod to use it. Splines is slower than the previous patch, but I did not notice any precision artifacts.

Removing Floating Point

• Apply RealityLost.patch to Files.Mod, Texts.Mod and the compiler.

• Recompile Files.Mod and rebuild the whole system (including the compiler):

  ORP.Compile Files.Mod/s Modules.Mod/s ~
  ORL.Link Modules ~
  ORL.Load Modules.bin ~
  
  ORP.Compile Input.Mod/s Display.Mod/s Viewers.Mod/s ~
  ORP.Compile Fonts.Mod/s Texts.Mod/s ~
  ORP.Compile Oberon.Mod/s ~
  ORP.Compile MenuViewers.Mod/s ~
  ORP.Compile TextFrames.Mod/s ~
  ORP.Compile System.Mod/s ~
  ORP.Compile Edit.Mod/s ~
  ORP.Compile ORS.Mod/s ORB.Mod/s ~
  ORP.Compile ORG.Mod/s ORP.Mod/s ~
  

• Restart the system.

Adding back Floating Point

• Revert the patch from above

• Apply RealityRegained.patch to the compiler.

• Recompile the compiler first:

  ORP.Compile ORS.Mod/s ORB.Mod/s ~
  ORP.Compile ORG.Mod/s ORP.Mod/s ~
  

• Restart the system

• Recompile Files.Mod and rebuild the whole system (including the compiler):

  ORP.Compile Files.Mod/s Modules.Mod/s ~
  ORL.Link Modules ~
  ORL.Load Modules.bin ~
  
  ORP.Compile Input.Mod/s Display.Mod/s Viewers.Mod/s ~
  ORP.Compile Fonts.Mod/s Texts.Mod/s ~
  ORP.Compile Oberon.Mod/s ~
  ORP.Compile MenuViewers.Mod/s ~
  ORP.Compile TextFrames.Mod/s ~
  ORP.Compile System.Mod/s ~
  ORP.Compile Edit.Mod/s ~
  ORP.Compile ORS.Mod/s ORB.Mod/s ~
  ORP.Compile ORG.Mod/s ORP.Mod/s ~
  

• Restart the system.