The same algorithm is applied to both eras of data, with adjustments for the individual instruments’ characteristics, but it is split into two datasets with different names that represent the two eras.

At the NASA Precipitation Processing System (PPS) the retrospective datasets are accessible with filenames that start with 2B.GPM.DPRGMI for GPM files and 2B.TRMM.PRTMI for TRMM files via:
HTTPS:   https://arthurhouhttps.pps.eosdis.nasa.gov/gpmdata/
STORM: https://storm.pps.eosdis.nasa.gov/storm/
 

At the NASA GES DISC the retrospective datasets are accessible via:              

GPM:    https://disc.gsfc.nasa.gov/datasets/GPM_2BCMB_07/summary
TRMM: https://disc.gsfc.nasa.gov/datasets/GPM_2BCMB_TRMM_07/summary

The near real-time datasets are also accessible at the PPS via: https://jsimpsonhttps.pps.eosdis.nasa.gov/combine/ or via FTPS.

For more information visit the GPM Data Directory, click on the "Level 2" tab, and scroll down to “2B Combined”.