Sinclair ZX Spectrum
The Sinclair ZX Spectrum is an 8-bit computer based on the Zilog Z80A microprocessor, manufactured by the British company Sinclair Research and released on April 23, 1982.
In Europe, the Sinclair ZX Spectrum was one of the most popular home microcomputers of the 1980s.
Its streamlined and compact design delighted thousands of computer and video game fans. Even today there are still thousands of Spectrum fans who continue to play their games (with emulators that load their tape dump files). There is also a collector's market for both original game tapes and the Spectrum themselves.
Sinclair ZX Spectrum
Features
Original ZX Spectrum features included:
- Zilog Z80A microprocessor to 3.5 MHz (8-bit databus and 16-bit address bus). Accompaniing the main processor was the ULA (Uncommitted Logic Array), responsible for performing auxiliary functions.
- Two RAM settings with 16 kB or 48 kB. The 16-bit directional limit is 64 kB.
- These 16 kB of ROM included an interpreter of BASIC SINCLAIR language developed by Nine Tiles Ltd. for Sinclair and that it was an evolution that they already developed for two previous commercial machines of the brand, the ZX80 and the ZX81, and of which the Spectrum is continuous. In the same memory area was also the ASCII character game that used the default machine (although it could be pointed to other memory zones and define alternative characters) and a reserved area just before the screen memory, ideal for EPROMs that could be connected in the rear slot.
- Rubber keyboard integrated into the computer in the 16 kB model and in the first 48 kB version. The original rubber keyboard oppressed two membranes with driver tracks that served to detect pressure. The ZX Spectrum Plus membrane had 3, this third layer widens the keys using the pressure of 2 contacts at the same time, to generate for example the quotes, these in the Spectrum 48K are performed by pressing SYMBOL SHIFT and P (on the Plus could also be performed in the same way). This membrane used to be the most fragile part of the computer and it was usual that over the years it was necessary to change it to several times.
- Storage system on common audio cassette tape. The data was accessed at a rate of 1500 bit/s. A 48 kB game took about half a little less than 4 minutes to load. There were games that used their own load system, called "turbo", at higher speed than the operating system standard on ROM, although slightly more likely to produce load errors. As an additional peripheral, from 1983 Sinclair put on sale the ZX Interface 1 which could be connected to up to eight quick-tape units called microdrive frequently used among software developers, which accessed the data at a speed of 120.000 bit/s (15 kB/s).
Later, a new case was developed, which consisted of an improved keyboard with hard keys and 4 layers of membrane, to allow the pressing of two function keys in one, and the more professional case, with square edges instead of rounded, which was called ZX Spectrum + (ZX Spectrum Plus). This development was also sold as an upgrade and used to be bundled with a 16 kB memory upgrade for Spectrums, which added a reset button and better cooling.
In short, the design of the computer was incredibly optimized and made the most of its seemingly small possibilities. All these features made the ZX Spectrum a very affordable and versatile piece of equipment, bringing microcomputing closer to a large number of people.
Graphic system
One of the peculiarities of the ZX Spectrum is its video system, being able to display a matrix of 256x192 pixels, but the color resolution was only 32x24, so groups of 8x8 pixels shared color information.
These color information or attributes consisted of: Background color or paper, ink color or ink, brightness attribute, and a flash attribute.
The background color is applied to pixels 0, and the ink color is applied to pixels 1 , each of which can be selected from seven colors.
The brightness attribute increased the brightness of colors (except black, which did not vary), so up to 15 colors could be displayed on the screen in total (seven times two brightness levels, plus the black)
The flash attribute caused the two background/ink color attributes to swap multiple times per second, giving a flashing effect.
So, we have 256x192 = 49152 bits = 6144 bytes for the bitmap (2048 bytes for each third of the screen) and 32x24 = 768 bytes for color, brightness, and flash, for a total of 6912 bytes.
The problem of having different resolutions for bitmap and color forced game programmers, especially during the later stages of the computer's life, to adopt ingenious solutions to minimize collisions between colors, a phenomenon known as " attribute clash" in the Anglo-Saxon world. This was because the ZX-Spectrum was not originally conceived as a video game machine. While the "attribute clash" allowed to reduce the size required for video to 6.75 kB, this made some of the displayed graphics look poor quality if the design was not thorough.
History and evolution
The hardware was designed by Richard Altwasser and the case and appearance is a design by Rick Dickinson. The software (ROM firmware) as well as the profuse instruction manual was the work of Steve Vickers. All of them had been involved in the design of Sinclair's previous models, the ZX80 and ZX81.
In April 1982 two models appeared: one with 16 Kb at a price of £125 (expandable to 48 Kb for £60) and another with 48 Kb from the factory for £175. With color image output and very acceptable sound, it stood out for its small size and its keyboard with hard rubber keys that maintained the traditional way of presenting complete words with keystrokes of previous models.
With such a tight price, especially compared to competitive models at the time, orders skyrocketed and Sinclair and the machine's assembly company, Timex, could not keep up. In July 1982 there were already 30,000 orders pending and at the end of August (due to the staff's summer holidays, which were scrupulously respected) there were already 40,000 delayed orders, with the consequent annoyance of many buyers. Clive Sinclair himself made a public apology in the media and promised to have the orders delivered in September of that same year, which he complied with.
By March 1983, more than 200,000 units of the ZX-Spectrum had been sold, and the home video game market had become a profitable phenomenon worldwide. Sinclair Research Ltd. became one of the strongest and most valuable companies in the industry today in just a few months. The price of their machines dropped to £99.95 for the ZX-Spectrum 16Kb, £129.95 for the ZX-Spectrum 48Kb and £39.95 for the previous model, the ZX81.
In 1981, Altwasser and Vickers parted ways with Sinclair to form their own company, which they would call Jupiter Cantab (an abbreviation for Cantabridgian). There they launched a machine of identical architecture to the one used in the company from which they came, the Jupiter Ace, which, however, had practically no impact (barely 5,000 units were marketed).
Peripherals
Over the years various peripherals appeared, such as proprietary storage devices (ZX Microdrive), disk interfaces (OPUS Discovery, DISCiPLE, Beta Disk), light pens, mice (AMX Mouse, Kempston Mouse, Star Mouse), printers (the ZX Printer appeared during 1983 at a starting price of £39.95), or game controls (joysticks) that could be connected directly, through the ZX Interface 2 or through other interfaces that came out later to market, such as those from Kempston Micro Electronics.
Software
The ZX Spectrum's software currently consists of over 20,000 titles. Although the ZX Spectrum's hardware imposed significant limits and restrictions, its software was highly diverse, including implementations of many programming languages, including them C, Pascal, Prolog (eg: micro-PROLOG), Modula-2, LISP, or Forth, various Z80 assemblers/disassemblers (eg: OCP Editor/Assembler, HiSoft Devpac, ZEUS Assembler, Artic Assembler), Sinclair BASIC compilers (eg: MCoder, COLT, HiSoft BASIC), Sinclair BASIC extensions (eg: Beta BASIC, Mega Basic), databases (eg: VU-File), word processors (eg: Tasword II), spreadsheets (eg: VU-Calc), graphic design programs (eg: OCP Art Studio, The Artist, Paintbox, Melbourne Draw), and 3D modeling (VU-3D), apart from, mainly, video games.
Other models
Sinclair ZX Spectrum +128
The Spectrum +128 was manufactured in Spain by Investrónica, the computer manufacturing and distribution subsidiary of El Corte Inglés, and official distributor of Sinclair Research. Investrónica had also distributed under its own brand (InvesDisk) a disk interface together with the TOS system for the ZX Spectrum, developed and marketed by Timex Computer, the Timex subsidiary in Portugal. The joint development is carried out at the Spanish headquarters and that is why in 1985 it first appeared in Spain.
The 128K model could work in either 48KB or 128KB mode. Most commercial programs ran in 48K mode, but in recent times commercial programs have appeared that are compatible with both versions. It featured an AY-3-8912 sound chip (the same one Timex would include in its Spectrum models a few years earlier), plus a small attached but separate numeric keypad, and a text editor built into the operating system firmware. However, in the English version, said numeric keyboard and the text editor were eliminated, introducing a set of menus into the operating system that would later be maintained by Amstrad models. Another exclusive feature for the Spanish market was the support of Spanish characters, being able to show both the letter eñe and the opening question mark and exclamation mark. The main reason for this change was a law that required all computers marketed in Spain to display these characters.
Internally, the 128 KB was divided into eight pages of 16 KB each, numbered 0 through 7. The Z80 processor's 64 KB of address space was also divided into four blocks of 16 KB each. Finally, the 32 KB of ROM was divided into two pages of 16 KB each, numbered 0 to 1. In the first block of the address space (addresses 0 to 16383) either of the two ROM pages could be selected; in the second block (addresses 16384 to 32767) was page 5 of RAM; in the third block (addresses 32768 to 49151) page 2 of RAM; finally, in the fourth block (addresses 49152 to 65535) could be any of the eight pages. When running a program in BASIC and in 48K mode, the active page was 0, and 7 was used as temporary memory for the BASIC and text editor. The only way to access RAM above 64KB was by using a "RAM Disk": a dummy disk on top of the extra RAM that allowed data to be instantly recorded and loaded.
In addition, the versions +2A/B and +3 incorporated extra modes that allowed to map RAM pages in the 64 kB addressable, thus being able to replace the ROM memory with RAM and have the entire address space. Four modes were available: Pages 0, 1, 2, and 3, Pages 4, 5, 6, and 7, Pages 4, 5, 6, and 3, and Pages 4, 7, 6, and 3. In addition, these models had 64 KB of ROM to be able to include the system disk (+3DOS).
Despite the changes, it was fairly compatible with the peripheral hardware developed for the 48KB models.
In games, especially when running in 128 mode, model enhancements such as multi-stage loading into RAM were available. In 48 kB only mode, memory mapping was disabled, so the AY-3-8912 chip was still usable, but the additional memory was not.
The graphics system included a double buffer system that allowed rendering memory to be selected between page 5 and page 7, which made it possible to instantly switch screens allowing some graphic tricks, such as being able to draw on the shadow screen and show it right after it has finished drawing, without showing how it was drawn progressively. This feature could be used to display graphics with more visual richness (by increasing the vertical resolution or emulating a larger graphics palette). Using this feature required the use of 13.5 kB of memory.
Amstrad Sinclair ZX Spectrum
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In 1986, the Sinclair Research Company sold the Sinclair trademark and its line of computer products to Amstrad for £5 million. From that moment Amstrad proceeded to bring the following models to the market:
- ZX Spectrum 128 +2 (1986), which incorporated in the same housing of the computer the cassette unit. It was dark grey and the ROMs were the same as those of the Sinclair ZX Spectrum 128 model, with some retouchings. It was more compatible with previous software than later models.
- ZX Spectrum 128 +3 (1987) with 3" disk drive incorporated into the same computer housing. This model recovered the traditional black color. It incorporated in 64Kb of ROM a disk operating system, the +3DOS. It also included an improvement of the BASIC Sinclair, the +3BASIC. The Locomotive Software company developed and commercialized a version of the CP/M operating system for +3.
- ZX Spectrum 128 +2A/B incorporating the +2 housing and +3 features; although they did not have the disk interface, they did include +3DOS and +3BASIC.
In 1992 Amstrad decided to withdraw the Spectrum models from the market, given the popularization of 16-bit and 32-bit machines.
Timex Sinclair Series
In mid-1982, Timex obtained the license to sell all Sinclair products in the United States, giving them the right to use their name for a 5% commission on sales and beginning to sell products under the Timex Sinclair brand that would eventually arrive. to be marketed through various subsidiaries also in Argentina, Poland and Portugal. The US affiliate released the Timex Sinclair 1000 and Timex Sinclair 1500 (both based on the Sinclair ZX81) and the Timex Sinclair 2068 (based on the ZX Spectrum). For its part, the Portuguese subsidiary launched the Timex Computer 2048 (also based on the ZX Spectrum) and the Timex Computer 2068 (based on the Timex Sinclair 2068). From this last machine, and as a result of an agreement between Polish Unimor and Timex Computer, the Unipolbrit Komputer 2086 was also developed only for the Polish market.
As an example of the differences between the Sinclair and Timex models, the TS2068 was launched at the end of 1983 (before the closure of the US subsidiary, in mid-1984), it is equipped with a port to put cartridges with software, two inputs for joysticks, an AY-3-8912 sound chip (the same one that would later be adopted for Sinclair and Amstrad 128Kb models), an 8KB ROM extension that included new commands for Sinclair BASIC, and two video modes: an extended 32x192 color mode (versus the Spectrum's original 32x24) and a 512x192 pixel monochrome mode. Within this line of improvements to the original Sinclair model, prototypes of an improved version, the Timex Computer 3256, were developed in 1987, which ultimately would not be released to the market.
The commercialization of the Timex Sinclair series computers would last until 1989, when Timex Computer of Portugal decided to exit the computer market.
Clonics and derivatives
In Europe, Asia and America, various clones were manufactured based on the successful Sinclair Research machine, such as the TK series (the TK 90X was its main representative) manufactured by the Brazilian company Microdigital or the Inves Spectrum of the Spanish Investrónica. In Argentina it was manufactured and marketed by the Czerweny company under the name of CZ Spectrum.
Some computers released by other companies and also based on the Z80 microprocessor (such as the Enterprise 128 or Tatung Einstein) also had peripherals that allowed Spectrum software to run on them.
In addition, Amstrad worked on the successor to the ZX Spectrum +3, called the "Loki" project. It was an 8-bit computer pushed to the limit, with support for more advanced video modes and memory comparable to that of a 16-bit computer. This project was never completed, due to the decline of 8-bit computers. In parallel, the company Miles Gordon Technology developed its own proposal as a successor, the SAM Coupé. With a 6 MHz Z80 processor and 256 KB of RAM, it included a 3.5" as a storage device.
In Western countries, after its withdrawal from the market in 1992, the Spectrum platform will persist mainly through emulator programs, although minor initiatives will emerge, such as interfaces for IDE hard drives, CompactFlash support, alternative operating systems or graphic expansions. At the end of 2014, the appearance of the Sinclair ZX Spectrum Vega, a video console based on the Spectrum, was announced.
In the countries of Eastern Europe several cloned computers of the Spectrum were developed in the 1990s, often with various extensions (Scorpion ZS 256, Pentagon 1024-SL, Kay 1024, Sprinter, ATM Turbo, Dubna 48K, Hobbit, Didaktik M, etc.).
In April 2017, the ZX Spectrum Next was launched through a Kickstarter campaign. It is an updated and expanded version of the original ZX Spectrum, developed using FPGA technology. The project produced two versions: The first consisted solely of the motherboard, based on the TBBlue project, which could be integrated into original ZX Spectrum cases and keyboards. The second version included a new case with a built-in keyboard, expressly designed by Rick Dickinson. At the end of 2017, the first part of the project was successfully completed, when the motherboards were shipped to users. After several delays and complications in industrial production, the final delivery of the keyboard version occurred in February 2020..
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