Hydra: loosely coupling the graphics pipeline to facilitate digital preservation.

It can be argued that software can be seen as a form of art and digital heritage and yet it rarely enjoys the same efforts afforded to it compared to physical counterparts. There are many reasons for this, such as the increasing costs of maintenance or the reducing amount of expertise in the specific aging technology. Maintaining software and ensuring that it continues to work on current hardware and operating systems is known as digital preservation. There are many ways in which we can attempt to preserve digital software and one of the most effective ones is by using emulation to simulate the obsolete hardware. However, for games and other entertainment media, this technique is not always effective due to a requirement on specific hardware, such as an accelerated GPU in order to reach an acceptable performance for the user. It is often difficult to emulate a GPU and, as such, a different approach often needs to be taken, which reduces the flexibility and portability of the emulation software. Hydra is a new approach to accessing the native hardware from within an emulated environment which allows for a much simpler emulator to be developed and maintained and yet also offers the potential of accessing other types of hardware without needing to modify the emulation software itself. Hydra is designed to be platform agnostic in that not only is it possible to integrate with existing emulators but also be immediately usable from within guest operating systems, ranging from legacy platforms such as MS-DOS, through to modern platforms such as the PlayStation 4 (Orbis OS, a FreeBSD derivative), through to more exotic platforms such as Plan 9 from Bell Laboratories. It can do this because it does not rely on a complex emulator-specific virtual driver stack. This PhD thesis provides the research undertaken for Hydra, including the motivation behind it, the specific problems it was designed to solve and how it can be implemented in a platform agnostic manner. Hydra’s performance is analysed to ascertain the suitability of the output to cater for, specifically, a wide variety of platforms that it can run on in a satisfactory manner within less powerful or emulated environments. A performance analysis study is conducted to ensure that the technology provides an acceptable solution to accessing preserved titles. This study concluded with results showing that Hydra offers a greater performance than software rendering, especially within emulated environments. A bandwidth comparison between Hydra and VNC was undertaken to ascertain the use of the technology as a streaming medium. The results concluded that under specific conditions, Hydra performed better than VNC by streaming at a higher resolution and consuming less bandwidth. Hydra is also utilised in a number of engineering tasks relating to preservation of software. The experiences of using Hydra in this way are discussed, including any difficulties encountered. Lastly, a conclusion is made and any future work is identified