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[MdaG]

I've been wondering why DOSbox takes up all that CPU power? Sure it's an entire OS on top of the running one, but still. Is MS-DOS that demanding? It could run well off of a 386 and with todays computers it shouldn't be that demanding. Or am I underestimating the complexity of the OS?

OS = Operating System

[bojster]

Well, it depends on how many cycles you set it to... However, I must agree that dosbox takes far more CPU power than dosemu or, if you prefer, works slower. But I think it's because it puts the emphasis on accuracy in emulating hardware (not only DOS) and that's the most CPU-consuming part. The best proof is that a lot of games work fine in dosbox, while only a few (though usually faster) in dosemu.

[Reup]

It's not MS-DOS that's demanding, it's the emulating that's demanding. DOSBox emulates the entire PC, with Soundcards, Mousedrivers, VESA etc. The guideline is that it takes about four times the amount of computer power of the emulated system to do a proper emulation. However, since the DOSBox emulator has to emulate the DOS Protected Mode, it takes up even more power. DOSBOx-site explaining this

[Data]

Reup is right.
dosbox is full pc emulator with it's own built-in dos.
Many parts take power away from the emulation of the cpu.
especially the emulation of the videocard.

[MdaG]

Aaaaah it's emulating an entire PC. Now I'm even more impressed by DOSbox.

[Rogue]

The easiest way to understand why is taking that much of CPU power and memory is to think how it all works.

For one cycle in real DOS machine, DOSBox emulates the same cycle plus video output, sound output, keyboard, joystick and mouse inputs, hard disk I/O, CD-Rom drive, plus it manages DOS memory. All of this requires a lot of work behind what we see, and that's why it takes so much power.

But if it takes all of your CPU (100%) then DOSBox will run slower, so you should adjust your cycles. Use this as guide on how to do it.