SANE, and Railroad Tycoon map generation

After we got the Railroad Tycoon main menu to work, we were able to proceed all the way until map generation. This part of the code uses Pack4 (FP68K) dispatcher to run some certain floating-point operations, so we had to implement the following SANE operations:

  • FINTX
  • FMULS
  • FDIVS
  • FS2X
  • FX2S
  • FI2X
  • FX2I
  • FL2X

The tricky part was, that SANE operates on 80-bit extended floating-point numbers, but modern CPUs use only 32- and 64-bit floating point numbers. Following the conventions Apple used in the SANE implementation for PowerPC, we convert the 80-bit extended numbers into 64-bit “double” values for calculation, and convert them to required destination format (depending on operation, usually the 80-bit extended) again.

Map of europe in Railroad Tycoon, after passing through map generation

I’m however not sure if the 80-bit conversion is correctly implemented at the moment, but it seems to work for now, as after adding these couple operations, we immediately got the map generator to pass through successfully:

Railroad Tycoon runs now successfully through map generation, until crashing at unimplemented List Manager dispatcher