An accidental classic, the acceleration mechanism of "Space Invaders" was actually due to the performance bottleneck of Intel 8080

The classic game in the history of video games, Space Invaders, was launched in 1978 and has always attracted many players with its unique mechanism. Zuhaitz, a programmer who claims to be a C/C++ expert, recently revealed that the game's exciting speed improvements are not due to superb programming, but to the hardware bottleneck of Intel's 8080 processor.

The game speed will also increase as the player kills aliens one by one, but the original Space Invaders code did not adjust the game speed. Zuhaitz pointed out in X that this phenomenon is actually a hardware accident, because the Intel 8080 processor can execute the game faster when the aliens are destroyed.

If you ever played Space Invaders you surely noticed that each time you killed an alien the game went faster.

But, if you checked the source code from one of the arcade machines, you would find nothing related to this. That’s because this mechanic is a hardware accident.

The… pic.twitter.com/UkqTEUvC9I

— Zuhaitz (@zuhaitz_dev) October 25, 2025

The 8080 processor was launched in 1974. It is the successor of the well-known 8008 and has a more powerful and flexible architecture. Although the performance was close to the limit at the time, it could still support 224×256 monochrome pixels in "Space Invaders". The game design also uses a specialized Fujitsu MB14241 image shifter and Texas Instruments SN76477 audio chip, but it cannot completely eliminate the processor performance bottleneck.

Zuhaitz pointed out that at the beginning of the game, changing the positions of 55 aliens, redrawing sprites, and checking collisions are very resource-intensive. This makes the game rhythm more compact and becomes the main attraction for players. Video game store owners can use this to attract a large number of players to keep investing money to play.

Later game versions and emulators will need to be adjusted to achieve the "machine-perfect gaming experience" that the original game is famous for when running on more modern and powerful platforms. Emulators such as MAME allow the execution of original code ROM, and limit the CPU clock and adjust the timer to maintain the same experience as the old architecture.

Intel 8080 bottleneck made classic 47-year-old Space Invaders arcade game run faster as enemies died — expert coder asserts ‘hardware accident’ to blame Further reading: Micro art reappears! Collector stitched together 216 photos to restore Intel's first 8-bit processor i8008