64-bit also provides better performance, that is if the hardware (CPU) supports 64-bit software, at least in theory. My understanding is that 64-bit CPUs have higher data throughput capacity than 32-bit CPUs. The game does choke sometimes especially during explosions or building collapses. Also if you like to play with a very high number of zombies, you might see a difference in performance between 32-bit and 64-bit versions. Your turns might take half a second instead of 3 seconds!
I can’t really testify on the performance differences, as I’ve only played 64-bit versions. 64-bit design decision could also be a safety measure against future unknowns - just to be sure that the game isn’t limited by the 32-bit limitations in the future. It might be called foresight. Who knows what sort of memory footprint CDDA has 10 years from now? 20 years? You wouldn’t want to start writing 64-bit versions of advanced 32-bit software far later down the road. Although I have no idea how challenging or laborous that 32-bit-to-64-bit transformation process is.
I doubt the game’s gonna run out of memory. On my PC the game’s memory load has stayed at around 350MB (the few times I have bothered to glance at it).
There’s really no reason to NOT go with 64-bit software design, right? I mean these days it’s just mercy and kindness to provide 32-bit versions just because 32-bit OSs can’t run 64-bit software, while 64-bit OSs CAN run 32-bit software, and 32-bit OSs aren’t produced anymore. 32-bit is legacy now …right? On the other hand, 32-bit CPUs are gonna be around for a long time, making sure there will always be a demand for 32-bit OSs and software because CPUs aren’t the first component to go bad in a computer.
Siding the matter, look at Dwarf Fortress as a warning example. It’s a single-thread application, meaning that it doesn’t benefit from multiple CPU cores. Although right now I’m not sure if multicore CPUs even existed when Dwarf Fortress was launched. My understanding is that you don’t transmute a single-thread application to a multi-thread version just like that. And now people have complained for a few years how DF stutters and stalls on their machines, especially the advanced and old fortresses. They call it “the FPS death”. And the developer, one man, is understandably reluctant to rewrite the whole game… Probably waiting for an easy way out, a future tech to save the day, while being fully aware that the further he develops the game, the more laborous a rewrite is going to be.
It more or less means you always gotta start a software project with the tech that provides the biggest room for expansion.
Edit:
Hasty look-up:
First dual-cores came out 2005 or after, depending how you view it: Pentium D, Athlon 64 x2.
Dwarf Fortress’s development started 2002. Alpha released 2006.