The 5120 integrated system was the last evolution of the 5100 and 5110 portable series, and the last 'heavy desktop' computer made by IBM.
The 5120 was an intermediate system between the IBM mainframes and the future 5150 PC. Actually, it was the first desktop Personal Computer made by IBM.
Basically, The 5120 technology remained the same as the 5100 model: same custom processor and same IBM typical hardware profile inspired by the mainframes technology.
The system featured a 9-inch monochrome moniteur (many 5100 users asked for a larger display) and two 8" floppy drives.
The system was sold with both APL and BASIC languages in ROM. APL allowed numerous business software written on IBM minicomputers to run on the 5120.
Bruce Franklin specifies:
After the IBM 5120, IBM manufactured another computer in Rochester based on the Intel 8088 chip that was called the DataMaster.
The computer's performance was poor compared to the 51XX computers, and IBM did not sell many of them.
Most people attribute the "IBM Personal Computer" as the first of what we know as PC's today, however IBM's model number for the PC introduced in 1981 was the IBM 5150. It was merely a new model of the 51XX line of computers and the second model to use an Intel processor.