这是steam一大佬对这种现象的解释
It's 100% an issue caused by the latest Nvidia drivers. (As far as I know, all versions that have come out since early December have been causing this issue in warband and no amount of reinstalling the latest drivers or reinstalling warband is going to solve your problem. Tweaking Nvidia control panel settings or tweaking Warband game settings isn't going to solve your problem either.)
The easiest way to solve the issue is to go to device manager and uninstall your display adapter. As you are doing that, make sure to tick the box that says "Delete the driver software for this device." Once you've deleted your graphics driver, you can just let your PC sit for a while, and Windows Updates should automatically download and install a special version of an Nvidia driver that GeForce Experience will call GeForce Game Ready Driver Version 432.00.
If you are unsatisfied with that version, you can go to the Nvidia website and download one of the older drivers. Try to pick one that was released before November 2020 just to be safe.
Anyway, yea, that's the only permanent solution to this problem right now. You can restart your computer and you'll be able to play like 30 minutes at a time before the problem becomes unbearable again. Save yourself the trouble and just uninstall your current Nvidia driver. Install an older stable version for now.
If you're REALLY a masochist and you want to keep playing warband without installing an older driver, just know that the lag/stuttering problem should only be happening while you are moving your mouse while the in-game cursor is present, so when you are on the campaign map, use WASD to move your camera around the campaign map and try to move your mouse the least amount possible.
This all has to do with the in-game cursor. You shouldn't be stuttering at all when you are inside of battle scenes, taverns, walking through towns, etc. The stuttering should only be occurring at instances where the in-game cursor is present and you start moving your mouse. (So this problem is mostly affecting you on the campaign map, in the inventory screen, in the party screen, basically any screen where the in-game cursor is present.)
You can easily test for yourself that this is purely in-game cursor and mouse movement related by restarting your PC, turning on your fps counter, launching Warband, and don't even bother playing the game. Literally just sit at the main menu and move your mouse non-stop for like 3 minutes and you will start seeing the drastic fps decline even though literally nothing is going on other than you moving the in-game cursor around the main menu. The more you move your mouse while the in-game cursor is present, the worse the stutter problem progressively becomes. It's not a time based issue, it seems to be a total amount of mouse movement input issue, and it only resets when you restart your PC.
