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High-level emulation, on the other hand, allows a system with complex hardware to be emulated on something only a bit more powerful. LLE is often limited to either much older systems, prototype emulators that are getting a handle on things, or lesser components of a system like an I/O controller. It also requires a system much more powerful than the original to run applications at the same speed.

Software-based emulation, however, requires intimate knowledge of the system or its parts, which may not be possible if documentation for it is scarce. However, hardware-based emulation isnвЂ™t always feasible as it adds cost to the system. Low-level emulation is one of the most accurate ways to simulate the system in question, since itвЂ™s replicating the behavior of the hardware. In fact, this is the most likely way the Xbox One can emulate the Xbox 360, despite running hardware that isnвЂ™t vastly superior to it. The performance HLEs can provide is such that it was possible to emulate the Nintendo 64 on a Pentium II processor in 1999, three years after the consoleвЂ™s release. This way of running an application is commonly known as just-in-time (JIT) compiling.

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Java code is not actually compiled and run natively on the host machine, but instead, the host machine runs an emulator of a theoretical Java machine. For example, command lists going to the emulated systemвЂ™s GPU can be intercepted and turned into DirectX or OpenGL commands for the hostвЂ™s video card to process.ДЄn example of an HLE is the Java Virtual Machine (JVM). The emulator can intercept the command list and turn it into something the host computer can process on a similar co-processor.

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These are a series of instructions that tell the co-processor what to do.

Lists interception: Co-processors, like the GPU and audio chip, that have enough hardware abstraction require the main processor to send command lists.

This is opposed to running each instruction one by one, which usually results in lookup overhead penalties.

Dynamic Recompiling: The emulator looks at chunks of the applicationвЂ™s processor instructions and sees if it can optimize them to run better on the host computerвЂ™s processor.

Interpreting: The emulator executes the applicationвЂ™s code line by line, by mimicking what each instruction is supposed to do.

HLE has three primary methods of simulating functions of the hardware. An HLE takes advantage of hardware abstraction by figuring out what the command(s) are intended to do in the emulated environment, and letting the host hardware do the rest. With hardware abstraction, the developer commands вЂњI want to read at this placeвЂќ and the firmware on the drive takes care of the rest. Originally, if a developer wanted to read data from a drive, they had to command the drive to spin up, position the read/write head, and get the timing down to read the data, pull the data, then transfer it over. An example is how storage drive interfaces came about. Instead, it provides a set of actions that a developer commonly uses and does all the little details automatically. Hardware abstraction is a way of hiding the intricate details of controlling hardware. This allowed for ease of programming as now developers didnвЂ™t have to invent and reinvent the wheel. In the mid-'90s, hardware abstraction was spreading to more computer systems, including video game consoles.

Instead of trying to simulate the hardware, it simulates the functions of the hardware. High-level emulation (HLE) takes a different approach to simulating a system.

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In high-level emulation, the PC provides software hooks so the game can run on its hardware.

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