How much of a performance drop could result from installing games on a HDD?

Any game that loads a lot of assets when switching between zones/levels will suffer. Games that load everything into memory all at once at the start are good to go. You will notice stutters/longer loading screens when switching between these storage reads, but moment to moment gameplay won't see much effect at all unless the developers were dumb enough to load assets from storage instead of memory constantly. I can't really pull specifics, but stuff like skyrim will literally be 5-10x faster at loading screens, loading a multiplayer map for a live service game also in that ballpark. Then again I had a terrible HDD at the time, if you have a modern one you should expect up to double, see below:

Depends on how often a game needs to access the disk and how much data it has to stream. For some games, you're not going to notice anything outside of longer load times. For others, it'll be a shitshow.

just play Sid Meier's Alpha Centauri

problem solved

Any game that predates SSDs or came out about 5 years after will be ok

does your mobo have a free m.2 socket? if so you can add a TB or 2 of holyfrickfast for like a hundred bucks.

my SN550's benchmarked at about 40x the speed of a HDD and real life performance reflects that, and those were technically already a generation behind 4 years ago when I got them.

I hate to be that guy but have you considered buying another SSD?

Really depends on the game and if it prefetches most stuff when it starts up so maybe you could be saving 3 seconds, 7 seconds or 12 seconds on a loading screen/start up.

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