page_title: TRS-80
section_title: Hardware
hierarchical_section_title: TRS-80 / Hardware
caption_attribution_description: English: Radio Shack Tandy TRS-80 Model I PCB
context_page_description: The TRS-80 Micro Computer System is a desktop microcomputer launched in 1977 and sold by Tandy Corporation through their RadioShack stores. The name is an abbreviation of Tandy/RadioShack, Z80 microprocessor. It is one of the earliest mass-produced and mass-marketed retail home computers.
  The TRS-80 has a full-stroke QWERTY keyboard, the Zilog Z80 processor, 4 KB DRAM standard memory, small size and desk footprint, floating-point Level I BASIC language interpreter in ROM, 64-character per line video monitor, and a starting price of US$600.
  A cassette tape drive for program storage was included in the original base package, but it proved slow and fiddly in practice. While the software environment was stable and capable, the fiddly program load/save process combined with keyboard bounce issues and a troublesome expansion interface contributed to the Model I's widespread reputation as something fun to tinker with for computer enthusiasts, but not well suited to serious use. As with many small computers of the era, it lacked full support for the ASCII character set, e.g. no lowercase letters, which also hampered business adoption.
context_section_description: The Model I combines the mainboard and keyboard into one unit, which became a design trend in the 8-bit microcomputer era, although the Model I has a separate power supply unit. It uses a Zilog Z80 processor clocked at 1.78 MHz (later models shipped with a Z80A). The initial Level I machines shipped in late 1977-early 1978 have only 4k of RAM. After the Expansion Interface and Level II BASIC were introduced in mid-1978, RAM configurations of 16k and up were offered (the first 16k was in the Model I itself and the remaining RAM in the EI).
  The OS ROMs, I/O area, video memory and OS work space occupy the first 16 kB of memory space on the Model I. The remaining 48 kB of the 64 kB memory map space is available for program use, subject to the amount of physical RAM installed. Although the Z80 CPU can use port-based I/O, the Model I's I/O is memory-mapped aside from the cassette tape and RS-232 serial ports.
caption: Tandy/RadioShack TRS‑80 Model I PCB
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