ZX Spectrum

Emulate the Sinclair ZX Spectrum home computer with Linux

Emulation is the practice of using a program (called an emulator) on a PC to mimic the behaviour of a home computer or a video game console, in order to play (usually retro) games on a computer.

Home computers were a class of microcomputers that entered the market in 1977 and became common during the 1980s. They were marketed to consumers as affordable and accessible computers that, for the first time, were intended for the use of a single non-technical user.

Back in the 1980s, home computers came to the forefront of teenagers’ minds. Specifically, the Amiga, ZX Spectrum, and Atari ST were extremely popular. They were hugely popular home computers targeted heavily towards games, but they also ran other types of software.

Sinclair ZX Spectrum
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The ZX Spectrum is an 8-bit personal home computer released in 1982 by Sinclair Research Ltd. The name highlighted the machine’s color capabilities, compared with its monochrome predecessor, the ZX81.

The Spectrum was ultimately released as eight different models, ranging from the entry level model with 16K RAM released in 1982 to the ZX Spectrum +3 with 128K RAM and built in floppy disk drive in 1987. The 16K model sold for £125 and the 48K model retailed at £175. That was significantly cheaper than the Commodore 64, which launched in the UK at £299, and the BBC Model B which retailed at £399.

The range sold more than 5 million units worldwide (and spawned many clones). It was among the first mainstream audience home computers in the UK, similar in significance to the Commodore 64 in the USA.

The Spectrum is based on a Zilog Z80A CPU running at 3.5 MHz. The original model Spectrum has 16K of ROM and either 16K or 48K of RAM, the latter being hugely more successful in terms of sales and range of games. Text is displayed using 32×24 characters. The image resolution is 256×192. To conserve memory, color is stored separate from the pixel bitmap in a low resolution, 32×24 grid overlay, corresponding to the character cells. In practice this means that all pixels of an 8×8 character block share one foreground color and one background color. The color conservation led to one of the Spectrum’s key flaws: color clash.

ZX Spectrum ROMs

The 16K ROM of the ZX Spectrum is a complicated Z80 machine code program. It’s divided into 3 main parts:

  • Input/Output routines;
  • BASIC interpreter;
  • Expression handling.

Amstrad owns the copyright on the ZX Spectrum ROMs, but they have given permission for ROM images to be modified and distributed for use with emulators, as long as the startup message contains the original copyright message.

Sinclair launched the ZX Spectrum with an unfinished ROM with a few well known bugs. There are also just over 1K spare bytes available which has enabled programmers to modify the ROM to create new features.

ZX Spectrum Emulators

ZEsarUX
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ZEsarUX is a free and open source emulator that supports all the Sinclair computers, not only the ZX Spectrum.

It offers almost perfect emulation of the range. It also supports non-Sinclair home computers such as the Amstrad CPC 464, MSX1 and Jupiter Ace. It’s our recommended open source emulator for the Spectrum.

Fuse is also a refined open source emulator with accurate 16K, 48K, 128K, +2, +2A and +3 emulation.

FBZX is an alternative Spectrum emulator, designed to work in FrameBuffer as well as X, both in full screen mode and in a window.

ZX Spectrum Software

The ZX Spectrum had a monster range of high quality games. There were a plethora of publishers who produced a whole series of classic games.

One such notable publisher was Ultimate Play the Game who developed a whole slew of classics such as Jetpac, Lunar Jetman, Atic Atac, Sabre Wulf, and KnightLore,  the latter used a forced-perspective isometric viewpoint branded Filmation. It was groundbreaking for the machine.

While games comprised the majority of commercial ZX Spectrum software, there were also programming language implementations (such as White Lightning), databases (such as VU-File), word processors (such as Tasword II, spreadsheets (such as VU-Calc), drawing and painting tools (such as Melbourne Draw, The Artist, and OCP Art Studio), and even 3D-modelling (VU-3D), and other genres. A few pop musicians even included Sinclair programs on their records.

Home Computers
ZX81Low-cost introduction to home computing notorious for its RAM pack wobble
Amstrad CPCCombined the computer, keyboard and data storage in a single unit
ZX SpectrumOne of the biggest selling home computers
Atari STA popular line of personal computers from Atari Corporation
Commodore 64Hugely popular home computer
BBC MicroSeries of computers designed and built by Acorn

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