To increase speed, this technique can be combined with the
Instead of trying to recompileĪll the code at once, do it on the fly when you encounter CALL or JUMP You may try combining static recompiler with an interpreter or a dynamicĭynamic recompilation is essentially the same thing as the static one,īut it occurs during program execution. Statically recompile self-modifying code as there is no way to tell The result will be a usual executable file which you can run on yourĬomputer without any special tools. In this technique, you take a program written in the emulated codeĪnd attempt to translate it into the assembly code of your computer. Interpretation takes a lot of CPU time and you may require a pretty fastĬomputer to run your code at a decent speed. The rest of your emulation to this cycle count).Ī single, big, and obvious weakness is the low perfomance. Of synchronization (you can simply count clock cycles passed and tie Virtues of this model include ease of debugging, portability, and ease The general algorithm for such emulator is following: It, and performs appropriate commands on the emulated registers, TheyĪn emulator reads emulated code from memory byte-by-byte, decodes There are three basic schemes which can be used for an emulator. What is "interpreting" emulator and how does it differ from "recompiling" It is illegal to distribute system ROMs (BIOS, etc.) with an emulator To emulate proprietary hardware, as long as the information on it Is it legal to emulate the proprietary hardware?Īlthough this matter lies in the "gray" area, it appears to be legal Graphics similar to the real arcade is a simulator. A Pacman game written for your computer but using Program imitating the Pacman arcade hardware and running real Pacman ROM Simulation is an attempt to imitate functions of a device.
What is "emulation" and how does it differ from "simulation"?Įmulation is an attempt to imitate the internal design of a device. The perfomance of such emulation may be very low though. It is necessary to note that you can emulate any computer system,Įven if it is very complex (such as Commodore Amiga computer, forĮxample). Only devices running more or less flexible program are interesting
So, you decided to write a software emulator? Very well, then thisĭocument may be of help to you. Of the HOWTO has been made by Daniel Campoverde. Same goes for anyįrequently asked questions that are not in this document.Īvailable, courtesy of Shun-Yuan Chou, andīy Guillaume Tuloup may or may not be available at the moment. You know any worth putting there, tell me about them. Important FTP/WWW addresses in the resources list in this document so if I do not answer toįlames, idiocy, and requests for ROM images though.
If you think that this document is missing something or want to make aĬorrection, feel free to email me your comments. It does have a pointer or two to the places where you can find
"compiling" ones, because I do not have much experience with recompilation Theĭocument mainly covers so-called "interpreting" emulators, as opposed to Text are mine alone and should not be taken for an absolute truth. Any opinions and advices contained in the following Who would like to write an emulator of one or another computer but do not
I wrote this document after receiving large amounts of email from people
How To Write a Computer Emulator by Marat Fayzullin