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When you think of an emulator, you probably think of something that allows you to play copies of games

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that you, of course, acquired in a totally legit way on a different system.

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So think a Game Boy emulator for your smartphone, or an N64 emulator for your desktop PC.

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And the fact that you need a special program to run these games makes intuitive sense, right?

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You're trying to run a game designed for a completely different piece of hardware.

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But hold on, because you need emulators for some of your old PC games too,

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even if you're trying to play them on another PC. I mean, sure, modern hardware is quite a bit faster than whatever you were using 20 years ago,

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but it still should be more or less compatible, shouldn't it? So why do you still need a program like, say, DOSBox to run your old game?

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Well, yes, we did give an overview of various reasons why new PCs often cannot run old games

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in this video. Right now, let's dig a little bit deeper and talk about why ostensibly compatible hardware

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can still require emulators. You see, back in the day, most computers used 16-bit architectures,

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both for their CPUs and operating systems, meaning that they handled data in 16-bit chunks and could address 2 to the 16th bytes of memory,

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so 64 kilobytes. This obviously wasn't very much, so later on, processors like the Intel 386

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introduced 32-bit computing, where systems could handle up to 4 gigabytes of memory.

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However, running old 16-bit software required a bit more work,

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as the transition to the 32-bit era introduced a couple of significant problems for older programs.

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One was that programs written for one architecture can't natively run on another.

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That is, a program written for a 16-bit system can't run on a 32-bit system without some tweaking.

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The other was that many 16-bit DOS applications ran in a processor mode called

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real mode, which allowed any program to access any portion of memory space,

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including portions of memory being used by other programs.

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This obviously meant that real mode had real security and stability issues,

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as there were no checks in place to make sure that a malicious or misbehaving program

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wouldn't get into other parts of the memory and threaten data or take down the system.

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So a new processor mode called protected mode became the norm in the mid-1980s,

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which isolated memory spaces from each other and gave programs different privileged levels

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to prevent programs that weren't device drivers or the operating system

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from executing certain instructions. However, lots of older programs could only operate in real mode.

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So combined with the 16- to 32-bit transition, 16-bit real mode had to be

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virtualized to a special mode called virtual 8086 mode that set up a virtual real mode.

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And yes, that's definitely an oxymoron. It's set it up by emulating an entire old-school 8086 processor.

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For a long time, having this capability was viewed as essential

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due to how common 16-bit programs were. Even in versions of Windows based on Windows NT, which didn't run on top of DOS,

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a built-in emulator called NTVDM allowed old-school DOS programs to run.

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NTVDM is present or can at least be installed in every 32-bit version of Windows NT,

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including Windows 10. However, NTVDM has its own issues such as low refresh rates, poor audio support,

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and an inability to slow down modern CPUs, which can make games run way too fast.

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But this still doesn't explain why old-school DOS games often won't run at all on new systems.

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The issue is that nowadays, most systems are shipping with 64-bit operating systems rather

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than 32-bit, primarily because they can support more than 4 gigabytes of memory.

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However, running a 64-bit OS requires an entirely new processing mode called long mode,

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which would have required Microsoft to build a whole new piece of software to virtualize a

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16-bit environment for running really old programs.

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And while 16-bit programs were still important when 32-bit computing became popular back when

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we were all using operating systems like Windows 95, they're basically considered obsolete in the

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modern era, so Microsoft simply did not bother re-engineering a built-in emulator.

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Therefore, 64-bit versions of Windows simply cannot run old DOS programs natively.

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So this is why, if you want to play old DOS games on your fancy new PC, you'll probably

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need a third-party emulator like DOSbox, that's had a lot more work put into it,

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with game support being a particular focus, making it a superior solution to NTVDM.

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And what's more, it's free. It's amazing how resourceful the gaming community can be when they're really determined to do

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Now if you'll excuse me, I've got a copy of the original Doom that's calling my name.

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So thanks for watching guys, like, subscribe, and be sure to hit us up in the comments with

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your own suggestions for what videos we should cover in the future.