ZX81 and family

Informations about ZX81 and clones

ZX80 - Micro Ace - ZX81 - TS1000 - TS1500 - CZ1000, CZ1500 - TK82, TK83, TK85 - PC8300, Power3000, Lambda - JUPITER ACE

Everyone knows about clones of IBM-PC, most of you will work with one of them. Some of you will remember those times when APPLE II- computers have been cloned. But do you know all members of the great ZX81 family? (I really don't know them all. Perhaps with your help we can find out more about this nice little computer and his family. Please look at the end of this text.) Like in real life, they all have their own identity. But they have some special characteristics, which will show us, that they all have the same background:
They all have been cheep and complete little computers, market in the first half of the eighties. Like in those days usual for home computers, their language was BASIC (with exception of Jupiter Ace), included in the ROM "operating system". Inflationary ROM and RAM-size was unknown. (By that way: turn your ZX81 upside down and read the label: It really is not a home computer, it is a PERSONAL COMPUTER = PC.)
The most important difference to all other home computers, and at the same time THE characteristic of the ZX-family is the lack of a special video-controller. This task is managed by the Z80 processor together with some very clever and at the same time very short soft- ware routines (less than 300 bytes) and a little hardware. Of course this is the reason why your ZX81 (in SLOW-mode) is a little bit slower than other home computers. Other common characteristics are:
- "keyboard" with 40 keys
- simple cassette port with about 300 bd
- busconnector with 46 (-2) connections
- 3.25 MHz CPU clock-frequency
- 9 Volts operating voltage
- TV connector for the use with a normal TV-set
- the B&W screen has 24 lines, each 32 characters long or in graphic-mode 48 X 64
- no ASCII code.
Despite of all these similaritys there are several differences, which may prevent that programms "SAVE"d from one member of the ZX81-family can be "LOAD"ed into an other. The reasons for this incompatibility are differences in: ROM-routines, system variables and display-file handling. But all BASIC-programs typed in keystroke for keystroke should work. (ZX81 and TS1000 are compatible)


This was the pedecessor of ZX81. It was the first computer sold for less than 100 Pounds. - 4 k ROM, 1 k RAM, only "FAST"-mode and integer BASIC


An american "pirate" version of ZX80 - 4 k ROM, 1 k RAM


One of the most popular home computers. (I say: THE BEST!!!!) - 8 k ROM, 1 k RAM, SLOW and FAST mode

TS1000 (TIMEX)

The american version of ZX81, with only some little differences: - 2 K RAM, shielded case, TV-output on channel 3 or 4


The argentinan version of TS1000 - 8 k ROM, 2 k RAM


The brazilian version of TS1000 - 8 k ROM, 2 k RAM

TS1500 (TIMEX)

Timex developped this improved version of TS1000 for the american market. - new CMOS-ULA chip, 16 k RAM (dyn.), new ROM, soft rubber keyboard


The argentinian version of TS1500


An improved version of TS1500 - 10 k ROM, 16 k RAM, joystick port, SPECTRUM-style case, two speed for SAVE and LOAD: 300 + 4200 bd

POWER 3000, LAMBDA, PC8300

Are these far east products identical? They have improved keyboard facilitys, you can type in each BASIC-command letter by letter, the soft rubber keyboard has two SHIFT and one RESET key.
- 8 k ROM, 2 k RAM, joystick port, monitor and TV output, sound
- A color-module (PAL) was sold for LAMBDA. It works on ZX81 too!
- Little changes in the character set for playing games.
- no RAM-delete after RESET


The Jupiter Ace has been developed by two former Sinclair empolyees, Steven Vickers and Richard Altwasser. The Jupiter Ace is the only known homecomputer with a FORTH-ROM.
- 8k ROM, 3K RAM: 1K each for programm, for the display file, for the character table
- like ZX80 it has no ULA-chip
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Peter Liebert-Adelt, Luetzowstr.3 D-38102 Braunschweig, Germany