Get best of the week

PS1 backward compatibility history on Sony Playstation 2


On March 4, we celebrated a jubilee date - 20 years have passed since the release of the PlayStation 2 in Japan, followed by sales in Europe and North America in the same year 2000. Without a doubt, all kinds of gaming media will publish lists and retrospectives in memory of one of the most successful and culturally significant consoles. Most likely, the focus will be on a variety of unique and diverse games that have contributed to turning the console into such a powerful force, but do not forget about one of the fundamental pillars of the system: backward compatibility with the vast majority of games from the library of the first PlayStation.

This feature, which was previously mainly found only in Nintendo portable consoles and some older Sega systems, made it possible to create a sense of interconnection between generations of equipment that had not often arisen in the console world before. She gave the PS2 a head start, which competitors could only envy. This was a legacy that was preserved to varying degrees in all subsequent Sony systems until the PlayStation 4, when Jim Ryan uttered the famous phrase in an interview with Time : “Who will play this?”, Refusing to satisfy consumers' demand for such technology.

How quickly the situation has changed in this regard.

Needless to say, due to Microsoft providing backward compatibility with the Xbox and Xbox 360, which became an important argument for the purchase of Xbox One, Sony's attitude towards this need has changed: now both companies are striving to implement backward compatibility in one form or another in their next consoles. Of course, all these efforts had to start somewhere, and for Sony the beginning was laid by a former engineer of the company, which you most likely have never heard of: Tetsua Iida.The story of Iida is curious: he was assigned the responsibility of developing backward compatibility of PS2 just a few years after joining the company, and in this work he is almost a novice. In 2018, he wrote a series of posts that described the painful way to implement this functionality, which he walked almost alone. On the 20th anniversary of the PS2 Japanese release, I am pleased to submit my translation of these posts. Most of the content has remained unchanged, including the images used, but in some sections I have provided additional clarifications received directly from the author. Also, the posts were slightly reformatted to make them more easily perceived as one post instead of the five original ones.

Be that as it may, I consider it an honor that I was given the opportunity to share with you this almost forgotten but very important story, because today backward compatibility and preservation of games in general are important for us, both from a cultural and scientific point of view. Although the fundamental concept was not invented by PS2, Iida’s work has definitely become an important catalyst for its popularization in the minds of most players. She allowed to keep relevance and accessibility of the history of games, without resorting to emulation on a PC. Without his direct participation, thousands of PS1 games would not have a second chance at life in the new millennium, and the gaming industry would have to spend more time studying its history, which has found its place in the present and in the future.

Tom James , Japanese-English translator


I developed a PS1 backward compatible emulator for Sony Computer Entertainment



In 1996, I got a job at Sony Computer Entertainment as part of a second wave of hiring newly graduated students. At that time, the SCE research and development department consisted of approximately 50 people. It was led by Ken Kutaragi, and guys like me were at the very bottom of the hierarchical ladder. If I'm not mistaken, I was hired right after Square entered the list of third-party Sony developers. Around the time Final Fantasy VII came out, I had the opportunity to see cutscenes from it. Like many, I still vividly recall the shock of seeing the untimely death of Iris ...

As far as I remember, my first task after joining SCE was to create a video converter code that received a video file at the input and applied filters to it. This application was my first professionally written program. The bottom line is that when I came to the department, I was his most useless employee. And I'm not exaggerating. I did not have real skills in designing electrical equipment and I did not even know how to run Windows 3.1, not to mention writing programs. Even today, I don’t understand what Sony management saw in me and why it decided to hire me.

Fortunately, thanks to the program being conducted at the company, I had the opportunity to learn how to program computers. It was easy for me to assimilate the material, and after this training I had the feeling that I could program anything. After completing the training, I did all sorts of things, they entrusted me with all kinds of work, from studying CD emulators to modeling data converters, libc, and much more. Around 1998, our entire department was invited to a short meeting about the next generation of the PlayStation system.

After that, the research and development department was divided into two teams. One team continued to work on the then-relevant hardware of the first PlayStation, while the other took up the next generation. I always liked to try new things, so I realized that I wanted to work in the second team. It seems that I was being interviewed for admission, because later, when I was sent to her, I was delighted.


As soon as I moved to the PlayStation 2 development team, I was assigned the task of realizing the possibility of launching games on the new system for PS1. At that time, the norm was that it was impossible to launch old games on new consoles, but SCE wanted to reverse this trend, which, in my opinion, was a far-sighted decision on the part of the company. Given the fact that at that time I worked in the company for only a few years, I was very flattered that I was assigned to work on such an important task.

When it was decided to implement backward compatibility of PS2 with games for PS1, there was already a plan to use the main PS1 processor as an input / output processor for new PS2 equipment. However, the subtlety was that no other PS1 equipment was planned to be used anymore, and this meant that everything else would have to be emulated programmatically. Until that moment, I was only working on software development, but I was tasked with writing an emulator for the PSU console SPU, that is, for its sound system.

The PS2 sound chip consists of two parts: the core and the digital signal processor (DSP). An experienced member of the team who worked on creating the sound system started emulating DSP, and I was assigned to work with the kernel. To do this, we took a room in the subcontractor’s office room and isolated ourselves from the rest of the world to write all the necessary code. There were no windows in the room, and I remember that in the process we often argued with my colleague. However, it was not so bad, as a result of joint work, we became very close friends.

I don’t remember exactly how we worked, but once our work was unceremoniously interrupted. As it turned out, the PS1 sound chip would eventually be added to the PS2 hardware list, which meant that all of our work could be thrown into the trash.


The SPU emulator that we wrote turned out to be useless, which is why our work hung in the air, because using the PS1 sound chip did not mean abandoning our own new PS2 sound processor. We thought about what we would have to do next, for example, to write test vectors for a new sound processor. However, my new assignment was a huge surprise.

I was assigned the task of emulating the PS1 GPU, and this greatly confused me. Someone else had to deal with this already, and when I asked what was happening, they told me that this person was leaving the company and I should continue his work without excuses. It is clear that the transition from working with sound to graphics has become a serious test for me. But in the end, it didn’t matter, because no one asked me. No matter how I relate to this, I had to obey the order.

I do not want to say that I perceived this task as impossible. I saw emulators as some kind of converters that receive instructions designed for older processors and translate them into code that the new processor can understand and execute. In this sense, even though the sound and graphics equipment are different, in general they only deal with the transfer of commands. All the emulator does is change the look and flow of these commands. If the emulator is fully tested, then in the end it should work, although in practice it will be difficult to implement.

By the time the work on GPU emulation was handed over to me, the previous developer, fortunately, had already laid the foundation, so I did not have to start from the very beginning. Therefore, first of all, I needed to understand the specifications of the GPU and PS1, and PS2. After that, I started implementing the missing instructions, because initially I tried to focus on reprogramming the PS1 console's GPU commands.

The first PS1 game to launch on the PS2 emulator was Ridge Racer. It was released simultaneously with the release of PS1, so it seemed very important that it should be launched the first of the entire library of games in the system. When I turned on the device, I realized the importance of making it the first PS2 game to be emulated.

The initial results were, to put it mildly, far from ideal. For example, the girl who started the race was rendered in the form of a mosaic, not a sprite. In addition, when the circle ended, the screen turned pink. Nevertheless, I was pleased that the game even started. Despite the fact that only the GPU was actually emulated, then I realized that we can achieve backward compatibility on PS2 with PS1 at this level of software emulation.


In the early morning hours of March 2, 1999, I stood behind the scenes of the Tokyo International Forum stage, where later that day at the PlayStation Meeting 1999 they were supposed to officially announce the development of PlayStation 2. My task was to demonstrate the console’s backward compatibility with PS1 after announcing this feature in presentation time.

I was ready from the night before preparing for the event. It has already been several months after the first launch of Ridge Racer, and great progress has been made in developing the GPU emulator. Now it was possible to run many games for PS1 on it, and the best of them was Crash Bandicoot: Warped. For this reason, it was chosen to demonstrate the PS2 backward compatibility features. There was only one problem: sometimes it hung during emulation.

Needless to say, serious problems would arise if the game hung in the middle of the demo in front of such a large audience. Unfortunately, I could not find the reasons for these failures. All that was possible to find out is that while Crash continues to move, the game remains stable for some reason. Knowing this, I did not sleep all night playing endlessly on the PS2 development kit. Fortunately, I was not alone, there was another person next to me who helped me through the game. The video transmission to our monitor was configured so that at the conference we could switch to the large screen on the stage with the click of a button. As you might have guessed, I played around with this switch, and it was very interesting. We could not just start the game in the morning, because there was a chance that the emulator itself would not load and we did not have enough time to fix it in place.Therefore, no matter how surprising it may sound, after starting it turned out to be safer not to turn off the system all night.

Fortunately, this night passed without incident. The event was approaching, and the system continued to work. The importance of this conference could not be overestimated. She was visited by Sony CEO Nobuyuki Ideas himself to support us. Technology demos showcasing the power of the Emotion Engine and Graphics Synthesizer of the PS2 system were demonstrated. From behind the curtains I could not really see what was happening. but I saw that people in the audience reacted positively to the presentation. Everything went according to plan. Finally, it’s time to announce the console’s backward compatibility.

Honestly, I almost do not remember what happened in these moments. It was planned that during the Crash Bandicoot demo I will play in the usual way, jump over obstacles and pass the level. But when the time came for the demonstration, I had big problems with the passage, and I constantly came across the same obstacle at the level. After that, my memories are completely empty. I can’t even say if I managed to go further.

However, in the end, everything seemed to go smoothly because, despite my poor demonstration, the announcement was greeted with applause. Everyone said that the event was a great success.


PlayStation 2 was released in Japan on March 4, 2000. Work on the PS1 emulator was generally completed around the New Year, if I'm not mistaken. In the end, there were several games that could not be made to work correctly, which is why the company released a public "black list" of games for PS1, which players can not play on the new console.

After the release of the system in Japan, it came to North America and Europe; Naturally, the games of these regions for PS1 were also supported by the emulator. Shortly before the release of regional versions, I came to Sony's American and European offices to help with debugging, and this was my first experience traveling abroad. As a result, PS2 was not 100% compatible with the PS1 catalog, but it supported almost all games. Remembering my work today, I believe that this was one of the most important tasks in my entire career.

Ken Kutaragi set a high standard for his team, he told us to always measure the quality of our work with respect to the best level in our class. When I think about what has met this bar in my life, the first thing that comes to my mind is my work on backward compatibility with PS1. That's how proud I am of her.

Frankly, perhaps I would not be able to deal with this alone, and during the work a lot of people helped me. If I could not cope with this, someone else would have done it. Nevertheless, the opportunity to observe such a large-scale project before its completion fills me with great pride. I can only hope that in my life I will have another such opportunity.

More articles:


All Articles