technology

Windows 95 included code specifically designed to run SimCity without bugs


If you’re over 30, chances are you’ve already got your hands on Windows 95. Released just as Jacques Chirac was beginning his first term as President of the Republic in France, OS from Microsoft was wildly successful. Its very low entry price, its graphic evolutions and its emphasis on program backward compatibility made it an essential OS of its time.

The importance of backwards compatibility

But this popularity took a lot of effort from the development teams, and a recently revealed example illustrates this perfectly. Kalyoshika, a podcast host dedicated to video games, recently re-shared an old blog post from the 2000s where it is detailed how Windows 95 embedded code specially designed to ensure the compatibility of the OS with the unbeatable game SimCity.

It’s hard to understand why Microsoft has gone to such lengths to ensure compatibility with this particular game if you don’t know the story behind it. SimCity. The game, then developed by the company Maxis (which will later integrate EA), was one of the first management games accessible to the general public. Its sandbox side, its total freedom of action and the fact that we could never finish it hoisted SimCity to the rank of flagship title in the history of video games, ensuring Maxis a colossal success. Only then, the first version of the game available on Microsoft’s OS had been developed for Windows 3.1, taking into account the technical characteristics of the system.

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The release of Windows 95 and its transition from a 16 to 32-bit architecture therefore broke compatibility with SimCity. As there was no question for Microsoft to release an OS incapable of running the most popular game of its time, the development teams had to be inventive. A piece of code solely dedicated to compatibility with the Maxis game has therefore been added to the OS. Its sole purpose was to scan the machine to see if the game was installed. If so, Windows would switch to a specific emulation mode each time the game was launched.

A bug present in SimCity

To be quite precise, the incompatibility of SimCity with Windows 95 was actually due to a bug in the game’s design. SimCity had an annoying habit of exploiting the computer’s virtual memory in unorthodox ways. The game was marking certain memory blocks as “free” when it actually needed them to run. This was not a problem on Windows 3.1, since this virtual memory was not allocated to anything else, but Windows 95 distributed this “free” memory much more dynamically. Results, SimCity crashed on the new Microsoft OS.

The company realized this in the early stages of development and therefore added this compatibility mode which did not release virtual memory immediately, leaving the game the possibility of functioning as on Windows 3.1. A hack no doubt, but symbolic of the importance that Microsoft attached to the backward compatibility of programs on Windows 95.

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