Rockwell Protocol Interface. An ASIC design first perpatuated by Rockwell Semiconductor, based on the idea that the modem could off-load the operations of data compression and error correction to the main processor, thereby making the modem electronics less complicated and therefor cheaper. First seen in the late '80 and existing into the mid '90s where it's legacy of being fucked by design was then carried in by todays' WinModem that we all love so dearly.