As part of the FPDoom project, a port of the Doom game for push-button phones based on the Spreadtrum SC6531 chip was prepared. Modifications of the Spreadtrum SC6531 chip occupy about half of the market of cheap push-button phones of Russian brands (as a rule, the rest are on MediaTek MT6261). The chip is based on the ARM926EJ-S processor with a frequency of 208 MHz (SC6531E) or 312 MHz (SC6531DA), the architecture of the ARMv5TEJ processor.
The complexity of porting is due to the following factors:
- There are no third party apps available on these phones.
- Small amount of RAM - only 4 megabytes (brands / sellers often indicate this as 32MB - but this is misleading, as they mean megabits, not megabytes).
- Closed documentation (you can only find a leak of an early and inferior version), so a lot was mined using the reverse engineering method.
At the moment, only a small part of the chip has been studied - USB, screen and keys, so you can only play on a phone connected to a computer with a USB cable (resources for the game are transferred from the computer), and there is no sound in the game. In its current form, the game is launched on 6 out of 9 tested phones based on the SC6531 chip. To put this chip into boot mode, you need to know which key to hold during boot (for the F + F256 model, this is the β*β key, for the Digma LINX B241, the βcenterβ key, for the F + Ezzy 4, the β1β key, for the Vertex M115 - "up", for Joy's S21 and Vertex C323 - "0").
Source: opennet.ru