Radio Shack introduced the the Model III as a replacement to the Model I in 1980. Unlike the Model I, the Model III was an all-in-one design; the monitor, keyboard, and disk drives were all in the same unit. This cut down on radio frequency interference and helped with school sales. ike the Model I, the Model III used a Z-80, but running at 2.0 MHz this time. The Model III was mostly software and hardware compatible with the Model I. Featuring a more powerful 14K Level II BASIC ROM, lowercase support, and had a numeric keypad built into the keyboard. The TRS-80 Model III could support up to 48K RAM internally, two internal drive bays, and with an optional floppy disk controller, operated in double-density by default.