Does slowdown in (g)zdoom look/feel the same way as vanilla?

[invictius]

I don't have a machine slow enough to test any iwad levels in, just wondering if zdoom with poor framerates when under load behaves the same way as those old machines with vanilla, e.g not what's going on under the hood but whether the framerate slowdown will look and feel similar.

Also applying the same thing to doom95, I'm guessing that and vanilla will slow down in a very similar way?

[KVELLER]

I'm not entirely sure, but AFAIK the DOS version didn't have frame skip, so having a low framerate meant you had a slow game. ZDoom and derivates have frame skip, so it'll try to keep the game running at the proper speed regardless of framerate (unless it's an extreme slowdown).

[Edward850]

11 minutes ago, KVELLER said:

I'm not entirely sure, but AFAIK the DOS version didn't have frame skip, so having a low framerate meant you had a slow game.

If it didn't have frame "skipping", its multiplayer wouldn't work at all. All Doom PC ports will process multiple gametics in a single cycle based on the amount of input collected since the last frame. This is derived from the networking logic that maintains/controls input creation and processing from the local and remote nodes, where the gametic processor waits until all inputs are received for a single frame, and will process multiple gametics to catch-up if enough inputs exist (for either performance or networking reasons). This behavior is directly derived from vanilla.

 

ZDoom keeps the same behavior, although actually has a bigger local input buffer so it can construct more player commands, resulting in more gametics processed between rendering if things slow down.