Microsoft used a 'USB Cart of Death' to debug early Windows PCs — the crash cart had 60 daisy-chained USB devices that would often trigger BSODs

In an entertaining new video previewed by Dave’s Garage, the design and purpose of Microsoft’s USB Cart of Death is discussed by two Windows development luminaries. The titular cart was based upon a mail cart, brimming with an unhealthy tangle of over 60 daisy-chained USB devices of all types and functions. Victimized PCs were connected to the cart via a single plug, often quickly falling prey to the infamous Blue Screen of Death (in the early days).

Dave’s Garage is hosted by Dave Plummer, who you may know for his important work on creating Windows Task Manager, Windows Pinball, Calc, and ZIP folders. Joining him in the video clip above is Raymond Chen, a veteran of Windows development for over 30 years and author of The Old New Thing.

Chen recalls that when USB was a new technology and began to get support in the Windows OS, its device diversity and flexibility made it imperative that it should be as robust as possible.

USB devices started to gain momentum from the Windows 98 era. Around this time, the Windows kernel team and other Windows developers needed to work on the robustness of USB support of Windows builds. Thus, the USB Cart of Death was born. Chen says that the cart was probably a repurposed office mail cart. However, it looked quite different as it was laden with the widest range of USB devices available in those early days.

Microsoft’s USB Cart of Death featured three mice, four keyboards, printers, drives, and all sorts of USB peripherals. Its creator(s) also added a bunch of hubs, and because the USB spec mentioned hubs could be daisy chained up to three deep, they did this, too. Overall, perhaps 64 USB devices were all chained together, aiming to push the interface to its maximum. Finally, as an ergonomic and fun touch, a USB gaming steering wheel was attached to the USB cart of death, with which its handler could steer it around.

With the cart constructed as outlined above, it was basically used to terrorize Windows developers. Chen told Plummer that the cart may be taken to a developer’s office, and the victim casually asked whether something could be plugged into a current test machine. “You plugged that one plug into the test machine [and] the entire USB infrastructure would go crazy,” recalled Chen.

The developer accompanying the cart might then wait for things to settle down and begin testing the various mice, keyboards, printers, etc, to see if they had all successfully been recognized. However, a ‘rude’ cart driver might instead plugin, watch the system start attempting to cope with ~64 devices being simultaneously foisted upon it, and then yank the plug amidst the PC’s struggle. “Because the usual result of this was a blue screen,” the cart got its nickname, the USB Cart of Death, explained Chen.

As well as surprising innocent and unexpecting developers, Chen said that the USB Cart of Death would sometimes be used to prepare BSOD PCs ready for debugging. He talked about a USB testing lab with rows of machines where he could plug/unplug the USB cart of death in randomly sadistic ways: five seconds – unplug, seven seconds – unplug, etc. The next morning, developers could come in and debug the crashed machines and hopefully make progress in stabilizing Windows USB support. Moreover, seeing PCs crash in different ways was both interesting and useful.

Chen quipped that after one USB bug was fixed, “it wouldn’t crash next time – the same way,” adding with some mirth, “Congratulations, it crashed for a different reason.”

Readers of a certain age might remember the USB plug-and-play scanner crash during Bill Gates’ presentation at Comdex. Chen reckons that Gates’ scanner crash with Windows 98 predates the USB Cart of Death. However, that on-stage upset might have inspired this four-wheeled USB device-packed menace, mused Chen.

Plummer’s full interview with Chen will be available via Dave’s Garage on YouTube starting Saturday, November 25.