This disclosure relates to caching SIM files at a baseband processor to reduce cellular bootup time. According to one embodiment, a wireless device may read SIM files from a SIM and store a local copy of each file in a cache of the baseband processor of the wireless device. SIM identification information for the SIM from which the cached files were read may be associated with the cache. Indicator information usable for comparing file versions may also be generated and stored in the cache for each file. Upon a subsequent SIM initialization, the wireless device may read SIM files from the cache instead of from the initialized SIM if the cached version is identical to the SIM version, which may be determined based at least in part on the SIM identification information and the indicator information for such files.