32-bit XP, always. 64-bit never went mainstream until the Windows 7 era. And 32-bit can run reasonably-well-behaved 16-bit software, e.g. 16-bit Windows games like SimCity 2000 or Civilization II.

That new a machine, you should put 16GB in it and dual-boot a 64-bit OS. That being said, isn't this machine at the very cutting edge for XP? Will that 980 run in XP without serious driver modding, etc?

Thanks for your comments! I am using this machine with 32bit XP, and it works like a dream (obtained the parts and specs per Phil's YouTube recommendation, using a modded nVIDIA drivers for my 980Ti), but I just wanted to see if I can run the 64bit version on it as well. (have a front loading SD 5 1/4 tray that I can easily remove different SSDs)

Best!

C0deHunter wrote on 2023-09-17, 22:32:

Thanks for your comments! I am using this machine with 32bit XP, and it works like a dream (obtained the parts and specs per Phil's YouTube recommendation, using a modded nVIDIA drivers for my 980Ti), but I just wanted to see if I can run the 64bit version on it as well. (have a front loading SD 5 1/4 tray that I can easily remove different SSDs)

If the goal is random experimentation with OSes not likely to be that useful, why not try? It's probably going to be more usable than playing with BeOS, OS/2 or NeXTSTEP or lots of other random OSes from history...

64bit xp is fine for xp gaming as long as you don't care about ntvdm (DOS and 16bit windows). On a i7 you should be using dosbox and vmware anyway. I used 2003 64bit for gaming back in the day and thats what xp 64bit is just with the shitty xp theme. With that said the amount of 64bit games that run on xp is very low (simply because most games were 32bit only) so you are better off dual booting xp 32 with a newer os if you want to play 64bit games.

There are a few x64 bit games that I wanted to try on x64bit WinXP.

C0deHunter wrote on 2023-09-18, 01:35:

There are a few x64 bit games that I wanted to try on x64bit WinXP.

And... for as long as your expectations are low, why not try?

(Did anybody write 64-bit games before, oh, 2010 or later?)

Crysis, UT2004 and Far Cry had builds. It was rather academic for the latter two though.

I played around with XP x64 a bit during its run. It's fine for most things but sometimes you might run into problems with games. I remember Oblivion doing something weird at some point. The testing just wasn't remotely as robust for consumer sorts of things (drivers/software) as compared to regular XP.

XP x64 was never really considered for anything let alone for gaming. It was all about XP x32 back then.

Windows XP x64 is a gimped Windows 2003 Server. You can skip it in favor of the latter.

C0deHunter wrote on 2023-09-17, 22:11:

Hello all, Building an XP retro gaming system, and need advice on choosing either 32bit or 64bit version of XP OS. […]
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Hello all,
Building an XP retro gaming system, and need advice on choosing either 32bit or 64bit version of XP OS.

Will be installing 2001~2013ish era games

System Spec:

ASrock B85 Killer MoBo
Intel i7-4790
4 (or for 64bit, 16GB) of DDR3 1600
nVIDIA 980Ti
X-Fi PCIe Platinum

Thanks in advance!

Dual-boot (maybe via physically swapping drives) 32bit WinXP and 64bit Win7, and you will have all bases covered.