Sinclair ZX Spectrum +3

The Sinclair ZX Spectrum +3 replaced cassette as the primary built-in storage with a 3-inch floppy drive. Its black case, full-travel keyboard, 128KB RAM and expanded 64KB ROM supported +3DOS and a revised BASIC while preserving 128K and 48K compatibility modes.

Disk access was dramatically faster and more reliable than tape, but the uncommon 3-inch format and changes to the expansion bus limited adoption and compatibility. The +3 was the most extensively equipped production Spectrum.

Notable Features

• Built-in 3-inch floppy drive stored approximately 180KB per side.
• +3DOS disk operating system was based on Locomotive's CP/M-derived AMSDOS technology.
• Parallel printer port supplemented the normal Spectrum connections.

Historical Significance

• The only mass-produced Sinclair Spectrum with an integrated disk drive.
• Represented Amstrad's effort to reposition the Spectrum as a more complete general-purpose computer.

Collector’s Notes

• Drive belts commonly fail, while blank 3-inch disks are less common than 3.5-inch media.
• The revised expansion connector omits signals required by some earlier peripherals.

Specifications

Technical Information
Name	Sinclair ZX Spectrum +3
Manufacturer	Sinclair Research Ltd
Launched	Monday, June 1, 1987
Launch Price	£249
Country	United Kingdom
CPU	Zilog Z80A at 3.5469 MHz
Units Sold
Operating System	+3DOS, +3 BASIC, 128 BASIC and 48 BASIC mode
I/O	RF, RGB, cassette, two joystick, parallel printer and expansion ports
Keyboard	Integrated full-travel keyboard
Storage	Built-in 3-inch floppy drive; cassette supported through external lead
Sound	AY-3-8912 three-channel sound plus beeper
Graphics	256 x 192 pixels; 15 colours with two screen banks
Display	32 x 24 characters
ROM	64KB in four 16KB pages
RAM	128KB bank-switched
CPU Speed	3.5469 MHz