
PCSX2 is the most complete Playstation 2 emulator to date. This project has been active for a long time, and the developers' efforts become evident in the latest versions. The emulator is capable of running Playstation 2 games at decent frame rates and it emulates every single feature of the original PS2 console.
The games are played with a keyboard by default, but PCSX2 has good support for other peripherals. If you want to do something really bizarre, you can get one of those Xbox 360 gamepads and use it with PCSX2. But most gamepads are supported.
The configuration screen is really not something intended for a novice user, but with some help, mostly everything can be customized. There is a console that displays all the information returned by the emulator, which comes in handy for troubleshooting. Out-of-the-box, the commercial games are not supported. To play those games you have to download a copy of the PS2 bios, which can't be distributed with the emulator for legal reasons. There is a compatibility list which shows the supported games and how playable they are. Most mainstream games play really well. Of course, the faster your computer is, the better results you will get.
In short, PCSX2 cannot be beaten. It is the most complete PS2 emulator out there, and even though it is not the most intuitive one, that is something you will have to live with. It isn't THAT hard after all.
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VirtualBox is an open source application to manage and run virtual machines. If you ever need to run a virtual (guest) operating system on your host machine that runs Windows, Linux, Mac OS X or Solaris operating system, you should check this program out.
It is absolute free but includes almost all the features that the modern virtual machines must have.
Innotek, the original developer of the software was bought out by Sun Microsystems. In early 2010, one of the top 100 Fortune companies, Oracle, bought out Sun and is now the current development curator of this application.
Given the open source nature of the software, it is expected that it is available for multiple platforms. One can download the program for absolutely free from the program's website. One can also find an extension pack available for a free download that enables the support of USB 2.0 and other technologies under guest operating system.
There are some bugs here and there, but if you check out the development logs, you can see that the developers address those bugs pretty quickly in hopes that they won't loose the already existing valuable customer base. There were only 5 months in between two major releases, so you can see that the ball is rolling and the application is not abandoned but evolving.
As far as the features go, the virtual machine market is very saturated with open source application, hence all of the VM developers are trying to keep up with the latest trends, giving the customers support for the latest technology. VirtualBox supports VT-x and AMD-v, therefore increasing the execution speed of your guest operating system. No word on supporting of VT-d, but I am sure it is coming in the near future, as the chips with that extension catch up the market. Keep in mind that using VirtualBox gives you an edge as it supports other virtual machine's hard drive images, such as VMWare's and Microsoft's, while the relationship is reciprocal due to close source nature of VMWare and Microsoft's products.
Overall, this application is one of the leaders on the market for virtualization. Its open- source nature gives it an edge over the closed source applications in regards to implementing the newest code and technologies.
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You must have heard about VMWare or Virtual PC; now, I will introduce you to Bochs. This is an open-source PC emulator written in C++. It can host different types of platforms based on different architectures.
It is released under GPL license.
This PC Emulator, not unlike others, emulates an Intel X86 computer, common I/O devices and BIOS. Bochs can be compiled for the emulation of a 386, 486, or Pentium CPU, either X86 or 64, including additional instructions for MMX, SSEx and 3Dnow!.
It can be run in different operating systems, such as Linux, DOS, or Windows (Vista and Windows 7 included, according to my tests). This software is mostly used for keeping the host operating system clean when you need to use some unreliable (or incompatible) software: when the virtual operating system fails, the host doesn’t. The program also emulates every single hardware part of a computer, such as hard drives, cdrom, and floppy drives (Bochs even allows you to add hardware if the emulation is already running).
However, it also should be noted that the emulation performance is somewhat slower than in other emulators. In addition, unlike other emulators, Bochs provides a much less intuitive GUI. Still, if you only need to run old games that refuse to run in your current operating system, Bochs could be your choice.
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ePSXe is one of the best Playstation emulators out there. It can only emulate Playstation 1 games. The application can emulate every aspect of a Playstation 1 with incredible accuracy.
If you have original CDs for your games (copies should work too), ePSXe will play the full game, let you save in virtual memory cards, play sound and even let you use gamepads on your computer.
Emulating Playstation games does take a little of computing power, but modern computers shouldn't have a problem doing it. In my own testing, I was able to play a few games I had chosen without any problems. The video wasn't slow at all and full 3D games played smoothly at all times. There is a multiplayer feature called netplay, which supposedly allows you to play with other people, but I couldn't get it to work.
Installation and configuration is a big deal with emulators of this kind. I am sure that all PSX emulators suffer from this problem. However, I should tell you that you are not going to be able to play games after you installed the app. You have to get a variety of files from the Internet and copy them in certain directories of the emulator for it to even finish the configuration wizard. The process isn't hard if you are Google-friendly. A couple of searches should do the trick. However, dead links are making it harder and harder to get the files that you need as the years go by.
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Download ePSXe PowerPack

Its emulation capabilities include graphics, sound, input devices, and quite a few memory mapping boards found in most USA games and a few popular Japanese boards. Jnes boasts an intuitive user interface, instant saves, and movie recording to making playing NES games more enjoyable.
One of the coolest features is the included database of Pro-Action-Replay and Game Genie cheats, courtesy of Gent.
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DOSBox is a DOS-emulator that uses the SDL-library which makes DOSBox very easy to port to different platforms. DOSBox has already been ported to many different platforms, such as Windows, BeOS, Linux, MacOS X...
DOSBox also emulates CPU:286/386 realmode/protected mode, Directory FileSystem/XMS/EMS, Tandy/Hercules/CGA/EGA/VGA/VESA graphics, a SoundBlaster/Gravis Ultra Sound card for excellent sound compatibility with older games...
You can "re-live" the good old days with the help of DOSBox, it can run plenty of the old classics that don't run on your new computer!
DOSBox is totally free of charge and OpenSource.
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QEMU is a generic and open source machine emulator and virtualizer.
When used as a machine emulator, QEMU can run OSes and programs made for one machine (e.g. an ARM board) on a different machine (e.g. your own PC). By using dynamic translation, it achieves very good performance.
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Dolphin is a Gamecube, Wii and Triforce emulator that provides users with the possibility of playing their favorite console games directly on a Windows machine. Most games run perfectly or with minor bugs. Games are playable at HD quality, with 1080p and more. This is a remarkable feature the actual Gamecube and Wii consoles are not capable of.
The program comes with multiple configuration screens concerning not only the main application, but also graphics, DSP, the Gamecube Pad and the Wiimote. It comes with Xbox 360 controller support, anti-aliasing and antisotropic filtering, a memory viewer and dumper, WAD support, a memory card manager and an action replay simulator.
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