Heh... Life's funny sometimes. A few minutes after posting this topic, I did some cause-and-effect thinking to try and imagine what might have changed since DOSBox was working properly. The message in the status console about how it's using the joystick tipped me off: I'd added a new joystick.

Sure enough, after deleting the joystick in my gaming devices, DOSBox started working perfectly again.

So, the question has changed... It's no longer "What's making DOSBox use 100% of my CPU?"; now it's "Why does DOSBox suddenly use 100% of my CPU when I have a joystick in my gaming devices?"

Hi,
There is something important to say : cycles are not the only factor wich affects CPU usage, the game itself can also affect it.
When you play a game, CPU usage varies and sometimes can be very high : it depends on the game in fact.

Does this problem occurs when you play a game or when you get prompt ?

PS. Sorry for my poor english... 🙁

H'lo,

Thanks for the reply... The problem occurs at all times, including when I am just at a prompt; I figured out that it happens only when I have a joystick configured in Windows, but now I'm trying to figure out how to fix it so I can have a joystick and still use DOSBox.

According to this thread : How to speed up DOSBox (by robertmo and mirekluza) it seems non-USB joysticks can severely slow down DOSBox.
Do you use a non-USB joystick ?

Hmm, interesting... Sure enough, yes, it's a non-USB joystick.

So it looks like this is a known issue... Presumably the DOSBox team knows about it and is working on it. I guess I'm not alone in this behavior. 😀

Thanks very much... Cheers!

it's not the dosbox teams problem.
it's sdl.
dosbox only delivers the message.