Ring and Tear: Doom Hacked on to Desktop Phones

Just as we were thinking there were no devices left to run Doom on, along comes another. This time, it’s a CaptionCall phone, a landline phone with a built-in voice-to-text system designed to help people with hearing loss. You can get one for free from the US government, so naturally there’s a thriving second-hand market on which they cost almost nothing. And they’re surprisingly powerful, as enterprising FPS player (and inveterate tinkerer) Joshumax discovered. 

Inside the CaptionCall’s unassuming charcoal gray exterior there lurks a quad-core ARM 7 i.MX 6 SoC, 1GB of DDR3, and 4GB of NAND flash. Those ARM cores are Cortex A9, and the only quad-core i.MX 6 model runs at 1.2 GHz. There’s a Vivante GPU attached, with four shaders, and a speed of 594 MHz, which is good enough for dual 1080p decoding.

The CaptionCall runs a form of Linux, but has its ports well secured, as Joshumax noted when he ran a port scan. Poking around inside revealed a UART port, which got him to a system console login prompt, but the root password was not evident. There’s a full explanation on Joshumax’s blog about how he cracked the password, dumped the kernel, extracted its ramdisk, and set about running Debian.

From there, via getting audio and Bluetooth working (though not the touchscreen, thanks to a bug), it was a single obvious step to running Doom on the phone’s seven-inch screen. If you’d like to have a go yourself, his code is on Github.