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TRS-80 Model III

26-1061 · 26-1062 · 26-1063 · 26-1066 · 1980–1984 · desktop

Specifications

Cpu: Zilog Z80A, 2.03 MHz
Ram: max: 48 KB on-board (no separate expansion box required, unlike the Model I) · base: 4 KB or 16 KB depending on configuration
Ports: Cassette in/out (built-in deck) · Expansion bus connector · RS-232 serial (on expanded/disk models) · Parallel printer port · Built-in monitor (integrated, not a separate port)
Display: Built-in monochrome monitor, 64x16 text (32x16 in wide mode), block graphics
Storage: base: Cassette tape via a built-in cassette deck (no internal storage) · options: One or two internal 5.25" floppy disk drives (single density, ~180 KB per disk), factory-installed
Os Support: latest: TRSDOS 1.3, with LDOS and Newdos/80 as popular third-party alternatives · shipped: Level I BASIC in ROM on cassette-only units; Model III Level II (Microsoft) BASIC in ROM on most configurations
Release Price: $699 (Level I, 4 KB, cassette only) to around $2,495 (16 KB, two disk drives)

Variants

Models

Level I (cassette)Entry configuration with 4 KB RAM, Level I BASIC in ROM, and no disk drives.

Storage

Model III with disk drives16 KB or 48 KB RAM with one or two internal 5.25" single density floppy drives and Level II BASIC, the configuration most business software assumed.

Upgrade paths

RAM

48 KB on the motherboard · Unlike the Model I, RAM expansion is on-board: no external Expansion Interface box is needed, just chip swaps and jumper changes.

~$100 for a RAM upgrade kit at the time

MODERATE

storage

Two internal 5.25" floppy drives, or up to two external drives via the expansion bus on some configurations · Drives mount inside the case next to the built-in monitor, a big convenience win over the Model I's separate Expansion Interface.

~$500 per internal drive kit at the time

MODERATE

other

Third-party 300 baud modem and RS-232 boards for telecommunications · Popular for BBS use once disk-based DOS variants like LDOS were running.

~$200 for a modem card

MODERATE