在创建了我自己的80年代BBC微型计算机模拟器(类型VBeeb到谷歌)后，有许多事情要知道。

You're not emulating the real thing as such, that would be a replica. Instead, you're emulating State. A good example is a calculator, the real thing has buttons, screen, case etc. But to emulate a calculator you only need to emulate whether buttons are up or down, which segments of LCD are on, etc. Basically, a set of numbers representing all the possible combinations of things that can change in a calculator. You only need the interface of the emulator to appear and behave like the real thing. The more convincing this is the closer the emulation is. What goes on behind the scenes can be anything you like. But, for ease of writing an emulator, there is a mental mapping that happens between the real system, i.e. chips, displays, keyboards, circuit boards, and the abstract computer code. To emulate a computer system, it's easiest to break it up into smaller chunks and emulate those chunks individually. Then string the whole lot together for the finished product. Much like a set of black boxes with inputs and outputs, which lends itself beautifully to object oriented programming. You can further subdivide these chunks to make life easier.

Practically speaking, you're generally looking to write for speed and fidelity of emulation. This is because software on the target system will (may) run more slowly than the original hardware on the source system. That may constrain the choice of programming language, compilers, target system etc. Further to that you have to circumscribe what you're prepared to emulate, for example its not necessary to emulate the voltage state of transistors in a microprocessor, but its probably necessary to emulate the state of the register set of the microprocessor. Generally speaking the smaller the level of detail of emulation, the more fidelity you'll get to the original system. Finally, information for older systems may be incomplete or non-existent. So getting hold of original equipment is essential, or at least prising apart another good emulator that someone else has written!

值得一看的是Imran Nazar尝试用JavaScript编写Gameboy模拟器。

我写过一篇关于用JavaScript模拟Chip-8系统的文章。

这是一个很好的开始，因为系统不是很复杂，但你仍然了解操作码、堆栈、寄存器等是如何工作的。

我将很快为NES写一篇更长的指南。

模拟器很难创建，因为有很多黑客(在不寻常的 效果)，时间问题，等等，你需要模拟。

有关示例，请参见http://queue.acm.org/detail.cfm?id=1755886。

这也会告诉你为什么你需要一个多ghz的CPU来模拟一个1MHz的CPU。

当你开发一个模拟器时，你是在解释系统正在运行的处理器组件(Z80、8080、PS CPU等)。

您还需要模拟系统拥有的所有外设(视频输出、控制器)。

你应该开始为简单的系统编写模拟器，比如旧的Game Boy(使用Z80处理器，我是不是没有弄错)或C64。

我知道这个问题有点老了，但我想在讨论中补充一些东西。这里的大多数答案都围绕模拟器解释它们所模拟的系统的机器指令。

然而，有一个非常著名的例外，称为“UltraHLE”(维基百科文章)。UltraHLE是有史以来最著名的模拟器之一，它模拟了商用任天堂64游戏(在家用电脑上表现不错)，当时人们普遍认为这是不可能的。事实上，当UltraHLE诞生时，任天堂还在为任天堂64制作新游戏!

这是我第一次在印刷杂志上看到关于模拟器的文章，而以前我只在网上看到过它们的讨论。

UltraHLE的概念是通过模拟C库调用而不是机器级调用来实现不可能。