HAPPY BIRTHDAY TO THE SINCLAIR ZX SPECTRUM!
Today, on St. George’s Day 2022, is the 40th Anniversary of the release of the Sinclair ZX Spectrum computer. It is a happy day to celebrate the Spectrum but a day also tinged with sadness after the death of the great British inventor and entrepreneur Sir Clive Sinclair in September 2021.
The Sinclair ZX Spectrum has been a very successful machine and has spawned thousands if not millions of British and international careers in information technology, games and other industries.
The Anniversary is being celebrated with an event at the National Museum of Computing at Bletchley Park. Sir Clive’s son Crispin will be attending.
40 years later, there is a thriving Spectrum scene with new games and software being released, repairs and refurbishments being done (including here at PopeyMon) and new models of Spectrum hardware with two new versions of the Spectrum Next.
And from conversations with customers, it is great that parents and grandparents are encouraging their friends and families to discover the wonders of the Spectrum rubber-keyed wonder.
I am often asked – how many types of Sinclair ZX Spectrum are there? And what are the differences and similarities between them?
So to commemorate the 40th Anniversary, I have written this article to answer these questions, with a (generally) chronological order of release of each model of Spectrum. Brief details of each model are given. The article is not meant to be exhaustive in technical detail. That will require more detailed articles on each model. There is a Glossary at the base of the article.
The Sinclair Era of Spectrum and The Amstrad Era of Spectrum
Broadly, the models of Sinclair ZX Spectrum fall into two categories – Sinclair-era and Amstrad-era. When Sinclair ran into financial difficulties, caused mostly by the Sinclair C5 and QL commercial failures, Alan Sugar’s Amstrad bought the Sinclair computer brand in 1986. I break the models of Spectrum into these two eras. And now there is a new era, of the Spectrum Next. This article does not discuss the Next.
In 1982 when it came to home computers in the UK, it was clear from the industry and from his biographies that Alan Sugar was The Apprentice and Clive Sinclair the Master. The Spectrum far outsold the Amstrad CPC in the UK and Sugar came into home computers when the Spectrum had already been established.
And the Spectrum and Amstrad computers would prove to be inextricably linked over time. Both would have varying successes in different parts of the world.
The Sinclair Era of Spectrum 1982-1986
The Rubber Keyed Wonder – the 16k and 48k Spectrum
It all started with the rubber key model that was released 40 years ago today, on 23rd April 1982. This was called Issue 1.
Before its release, the Spectrum had also been called the ZX82. Its predecessors were the ZX81 and ZX80. Sinclair’s Mark 14 computer could also be called another Sinclair ancestor of the Spectrum.
In a nutshell, the Spectrum is a Z80 CPU-based microcomputer with a custom ROM implementing the Sinclair BASIC operating system and assisted by a Ferranti ULA chip. It could be viewed the other way around, with the ULA being the beating heart of the Spectrum.
The Spectrum ULA deals with input and output including:
- the RF display output to UHF Channel 36 on a domestic TV
- the rubber keyboard with membrane and
- using cassette tape for loading and saving programs to an external tape unit.
The Spectrum came in 16k RAM and 48k RAM models. The 16k could be upgraded to 48k at a later date. There was a special board at first for the Issue 1 board and eventually with the Issue 2 board, it could be done with the addition of 8 upper RAM chips and two wire links on the board.
I offer the 48k upgrade service in the PopeyMon Webshop. I can also reverse the process for you, if you want to revert a 48k Spectrum back to 16k.
There were 8 revisions of the board inside the rubber key case:
- Issue 2
- Issue 3
- Issue 3B
- Issue 4A
- Issue 4B
- Issue 4S
- Issue 5
- Issue 6A
Each issue made changes to the printed circuit board (PCB) design and added, removed or modified some components.
The power circuit that creates the voltages needed for the Spectrum from the external power supply unit (PSU) proved to be unreliable and 40 years later still causes many problems for Spectrum users. This DC-DC conversion circuit was tweaked but remains problematic 40 years later.
In the PopeyMon Test, Assess and Repair service that you can buy in the PopeyMon Webshop, it often comes up during testing and assessing as the cause of problems with my customers’ Spectrums. I have written an article on the common problems with the Spectrum – the keyboard membranes also dry out and need replacing. I can also supply and fit them for you.
The Spectrum +
The Spectrum case and keyboard did not change until the Spectrum + model which was released in 1984. The Spectrum + had the same board but put inside a new black case with hard keys, some extra keys and a slightly different layout. It also had spring-loaded legs and a reset button fitted inside.
Any Issue board from the rubber key model can be fitted inside the Spectrum + case. It is the same board.
The 128k Spectrum – a.k.a. Toastrack
The next model of the Spectrum was the Sinclair ZX Spectrum + 128k, shortened to the “Toastrack” due to the huge black heat sink protruding from the right-hand-side of the case.
Other than the heat sink, the case is very similar to the Spectrum + case with the keyboard and membrane being identical to the Spectrum + and with the same reset button.
As well as adding RAM, there were other changes to the software and hardware that included:
- a new AY-3-8912 sound chip
- RGB TV output as well as the traditional RF
- a MIDI music port
- a new ROM and menu system allowing 128k and 48k modes, plus tape Loader and Calculator options on the menu
The Amstrad Era of Spectrum From 1986 Onwards
The Sinclair 128k ZX Spectrum +2 (Grey Model)
When Amstrad took on the Spectrum, they hastily produced an Amstrad flavour on the Toastrack theme. They used the case design and philosophy of the Amstrad CPC 464 and added a built-in Datacorder to the case and a “proper” full keyboard. The new model looked like a CPC 464 but was essentially a Toastrack Spectrum inside.
With deadlines looming, commercial decisions were made to add features with a typically Sugar-esque flavour. Some of these would prove to be very annoying to users of the Sinclair-era Spectrum models then and now.
- manufacturing was eventually to be moved from the UK and go to Taiwan with the Grey +2 and eventually China with the Black +2. The early issue Grey +2 was made in the UK with the later production moved to Taiwan.
- joystick ports were added although to an Amstrad standard not the Atari standard
- printer port was added
- RS232 and AUX ports were added. The AUX port could be used with a light gun.
- RGB output was retained
- MIDI port was retained
Only minor changes were made to the ROM such as the copyright and menus.
The Black Tape +2 Model and +3 Disk Model
This was a radical re-design of the Spectrum with a dark grey/black case instead of the Grey +2 case. As with the later versions of the Amstrad CPC computers, the number of chips would be reduced.
The interfaces remained the same, but the board inside was a complete re-design of the 128k Spectrum PCB. A new Gate Array chip would be soldered “in a hole” on the new Spectrum board, and not using through-hole soldering. The Amstrad 40077 part number was allocated to it and it was primarily this 40077 IC that allowed the reduction of chips.
There was a tape (Datacorder) model, the +2A and also a 3 inch disk version, the +3. Again, the Amstrad CPC computer had its influence on the Spectrum. The CPC 6128 also had a 3 inch disk drive.
The re-design also removed the notoriously unreliable power (DC-DC conversion) circuit. A large power brick would be used instead, like the later Commodore Amiga and much later Microsoft Xbox power suppllies. The required voltages would be generated inside the PSU now, and not on the new Spectrum PCB.
With a re-design there are inevitability compatibility issues. While these are limited, they do cause issues with a very small number of programs.
There were later revisions of the Black +2 and +3, being called the +2B and +3B.
By then, production had been moved by Amstrad to China.
Production of the Spectrum ceased in the early 1990s.
I offer services for ALL models of Spectrum in the PopeyMon Webshop. I also sell parts.
Please browse the PopeyMon Webshop and get in touch if you have any questions or are looking for a bundle of Spectrum goodies.
HAPPY BIRTHDAY TO THE SINCLAIR ZX SPECTRUM!
Finally, to answer the question in the title of the article…
According to the definitions of model that I have used in this article, there are…
SIX models of Sinclair ZX Spectrum over two eras.
- rubber keyed 16k/48k
- Spectrum +
- 128k Spectrum “Toastrack”
- Grey +2
- Black +2A/+2B tape model
- Black +3/+3B disk drive model
But technically, there are other ways of looking at the question, so like the very large computer Big Thought in Douglas Adams’ Hitchhikers’ Guide to the Galaxy, the answer (42) depends on (being more specific in) the question.
This article is just one Spectrum fans’ view and classification, after all. You could say that there is only one type of Sinclair ZX Spectrum – the Spectrum! 🙂
I hope that you found the article interesting and informative, and this will encourage you to buy products and services in the PopeyMon Webshop and PopeyMon eBay Shop and read more articles on the PopeyMon website.
Happy Spectrum-ing to all!
CPC Amstrad Colour Personal Computer
DC Direct Current of electricity
IC Integrated Circuit chip
MIDI Music Industry Digital Interface
PCB Printed Circuit Board
PSU Power Supply Unit
RAM Random Access Memory
ROM Read-Only Memory
RGB Red-Green-Blue standard for computer displays
ULA The Ferranti Uncommitted Logic Array integrated circuit chip