The TK85 was a

ZX81 The ZX81 is a home computer that was produced by Sinclair Research and manufactured in Dundee, Scotland, by Timex Corporation. It was launched in the United Kingdom in March 1981 as the successor to Sinclair's ZX80 and designed to be a low-cost ...

clone made by

Microdigital Eletrônica Microdigital Eletrônica Ltda. was an influential Brazilian computer company in the 1980s, based in São Paulo. History Established in 1981 by the brothers George and Tomas Kovari (whose initials were the TK of the domestic computers line ma ...

, a computer company located in

Brazil Brazil ( pt, Brasil; ), officially the Federative Republic of Brazil (Portuguese: ), is the largest country in both South America and Latin America. At and with over 217 million people, Brazil is the world's fifth-largest country by area ...

. It came with 16 or 48 KB RAM, and had a

ZX Spectrum The ZX Spectrum () is an 8-bit computing, 8-bit home computer that was developed by Sinclair Research. It was released in the United Kingdom on 23 April 1982, and became Britain's best-selling microcomputer. Referred to during development as t ...

–style case, similar to a ''

Timex Sinclair 1500 The Timex Sinclair 1000 (or T/S 1000) was the first computer produced by Timex Sinclair, a joint venture between Timex Corporation and Sinclair Research. It was launched in July 1982, with a US sales price of US$99.95, making it the cheapest hom ...

''. Unlike the ZX81, the TK85 used discrete logic circuits instead of a ULA, and during manufacture, several chips were scraped so that competitors couldn't copy the circuit. The circuit board had space for a

AY-3-8912 The AY-3-8910 is a 3-voice programmable sound generator (PSG) designed by General Instrument in 1978, initially for use with their 16-bit CP1610 or one of the PIC1650 series of 8-bit microcomputers. The AY-3-8910 and its variants were used i ...

sound generator chip (compatible with the ZonX-81 sound board), and although none came factory installed, it is possible to add the necessary circuits. The TK85 came with a copy of the 8K ZX81 floating point BASIC, and an additional 2K EPROM, mapped to addresses 8192-10240, containing machine code routines for use with tape files. These routines could save (HISAVE), load (HILOAD) and verify (HIVERIFY) in "Hi-Speed" (4200 bps); save and load, BASIC variables in 300 bps (standard ZX81 speed) using DSAVE and DLOAD functions and 4200 bps (Hi-Speed) using DHSAVE and DHLOAD. These routines were all accessible using RAND USR commands. The save to variable function could be used to make copies of programs on tape. The expansion port on the back of the computer is compatible with the ZX81, although some peripherals may not work due to conflicts with the 2K of extra ROM. The rear of the computer featured a TV output (without video backporch), EAR and MIC sockets for connecting to an external tape recorder, a joystick port using a DIN socket (that simulated the 5,6,7,8 and 0 keys), a ZX81 Compatible expansion port, space for a sound output socket, and a socket for the 9V external power supply. Since the joystick used the cursor keys, and due to the circuitry for the keyboard, it wasn't possible to detect diagonal directions correctly.

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Microdigital TK85
Microdigital Eletrônica Goods manufactured in Brazil Sinclair computers and derivatives {{Compu-hardware-stub