Tilt! Ex-Microsoft coder explains bug in Windows 3D Pinball that hogged CPU and ran at 5000 FPS

Dave Plummer, one of the more famous ex-Microsoft employees out there who has his own well-trafficked YouTube channel, has been talking about the worst bug he was ever responsible for as a software engineer - and it was in a pinball game.

Plummer - who was responsible for Task Manager in Windows, and also bringing in ZIP support, to name a couple of highlights in a long programming career - told his latest tale in the above clip on his Dave's Attic channel, as pointed out by The Register.

The bug in question was in the Windows NT port of 3D Pinball (Space Cadet) and was present in the engine Plummer wrote around the original code to deal with the video and audio.

Plummer observes:

"My game engine had a bug in that it would just draw frames as fast as it could."

The CPUs at the time, running at 200MHz or so, would run the game at 60 FPS to 90 FPS which was obviously fine - but as more modern CPUs came in, the unlimited ceiling for the frame rate became a problem.

Plummer explains:

"It was now drawing at, like, 5,000 frames per second because machines were much, much faster."

It took another Microsoft software tinkerer, Raymond Chen, to find the bug, and add a frame rate limiter to prevent the huge escalation in FPS from happening. With the limiter in place, 3D Pinball stopped tying up an entire CPU core, and processor usage for the game dropped to 1%.

As Chen notes:

"My proudest moment in Windows development was I fixed Pinball so you could kick off a build and play Pinball at the same time."

All of this rather reminds me of Amazon's New World MMO and the issues that game had with hugely spiking frame rates at the menu screen actually melting some high-end GPUs. (Although this turned out to be a hardware issue with said graphics cards, brought on by the game's uncapped frame rate).