website/content/museum/microdigital-tk-90x.md

---
title: Microdigital TK-90X
categories:
- Computers
types:
- Home Computer
origins:
- Brazil
years:
- '1985'
cpus:
- Z80A
params:
  name: TK-90X
  company: /companies/microdigital
  company_name: Microdigital
  specs:
  - label: NAME
    value: TK-90X
  - label: MANUFACTURER
    value: Microdigital
  - label: TYPE
    value: Home Computer
  - label: ORIGIN
    value: Brazil
  - label: YEAR
    value: '1985'
  - label: BUILT IN LANGUAGE
    value: Sinclair BASIC
  - label: KEYBOARD
    value: Rubber keyboard - 40 keys
  - label: CPU
    value: Z80A
  - label: SPEED
    value: 3.58 MHz
  - label: RAM
    value: 16K and 48K versions
  - label: ROM
    value: 16 KB
  - label: TEXT MODES
    value: 32 chars. x 24 lines
  - label: GRAPHIC MODES
    value: 256 x 192 dots
  - label: COLORS
    value: 8 with two tones each (normal and bright)
  - label: SOUND
    value: 1 voice / 10 octaves (via TV set)
  - label: SIZE / WEIGHT
    value: Unknown
  - label: I/O PORTS
    value: Expansion port, tape-recorder (1200 bauds), RF video out, Joystick
  - label: POWER SUPPLY
    value: External 9V DC power supply unit
  - label: PERIPHERALS
    value: Sinclair (not all) and third sources peripherals
  - label: PRICE
    value: |-
      16K Cruzeiros 1.499.000, US$ 214 (1985)\
      48K Cruzeiros 1.749.000, US$ 249
  tabs:
  - photos
  - links
  photos:
  - title: TK90X
    subtitle: ''
    text: thanks to Thomas Conté for this picture
    image: null
  - title: TOP
    subtitle: ''
    text: ''
    image: null
  - title: 'KEYBOARD CLOSE-UP #1'
    subtitle: ''
    text: ''
    image: null
  - title: 'KEYBOARD CLOSE-UP #2'
    subtitle: ''
    text: ''
    image: null
  - title: 'CLOSE-UP #3'
    subtitle: ''
    text: Thomas Conté
    image: null
  - title: KEYBOARD PARTS
    subtitle: ''
    text: the keyboard is made of a sheet of rubber including all the keys, placed onto a printed circuit. When a key is pressed, a small conductive washer located below each key touches the circuit board and connects two tracks.
    image: null
  - title: REAR SIDE
    subtitle: ''
    text: |-
      From left to right:\
      • DC power connector\
      • Expansion connector\
      • 9-pin joystick connector\
      • Tape recorder In/Out jacks\
      • RF video output to TV set
    image: null
  - title: CONNECTORS CLOSE-UP
    subtitle: ''
    text: thanks to Thomas Conté for this picture
    image: null
  - title: BOTTOM SIDE LABELS
    subtitle: ''
    text: ''
    image: null
  - title: MAIN BOARD
    subtitle: ''
    text: |-
      **(1)** RF modulator and chinch jack\
      **(2)** Tape recorder In/Out jacks\
      **(3)** Joystick DB9 plug\
      **(4)** Extension connector\
      **(5)** 5V DC power regulator\
      **(6)** External 9V DC jack\
      **(7)** I/O chip\
      **(8)** Keyboard connector\
      **(9)** Zilog Z80A processor\
      **(10)** Seems to be a copy a the Spectrum ULA custom chip (more info needed!)\
      **(11)** 48 KB RAM chips. The RAM chips are separated in two banks, 16KB in 8x4116 chips shared with video on a separated bus (framed) and 32KB in 4x4416 chips (right side of the frame)
    image: null
  - title: MAIN BOARD CLOSE-UP
    subtitle: ''
    text: Custom chip and Z80A processor.
    image: null
  links:
  - title: Clube do TK90X
    url: http://www.tk90x.com.br
    text: Brazilian site dedicated to the TK90 and other Microdigital systems
  - title: Here, you can buy several Didaktik models and peripherals.
    url: http://www.kompaktservis.cz
    text: Site in Czech language. Try e-mail
  - title: Home Computer Museum
    url: http://www.homecomputer.de/pages/f_sinclair.html
    text: Stephan has a lot of Spectrum clones with wonderful pictures
  - title: Sinclair Nostalgia Products
    url: http://www.algonet.se/~rsm/zx/zxclones.html
    text: Impressive list of ZX Spectrum clones with useful infos
  - title: ZX Spectrum in the 21st Century
    url: http://tarjan.uw.hu/zxclones_en.htm
    text: Nice review of modern Spectrum clones
  comments:
  - author: Diogo patrão (Brasil)
    date: Saturday 11th April 2020
    text: It also featured an extra BASIC command, UDG. UDG 1 changed to the character set with portuguese and spanish characters (such as ã, ç) , and UDG 2 called a character editor!
  - author: Marcelo Santos (Sao Paulo / Brazil)
    date: Tuesday 10th June 2008
    text: Hey, is there any other version of the board? I had one of these, and I changed the ROM version and it was running a genuine ZX Spectrum ROM. But funny I don't remember where the hell is the slot... Looking at the pictures, seems to me that in the place that is the I/O chip, it used to be the ROM eprom. Can anybody help me?
  related:
  - /museum/didaktik-gama
  - /museum/didaktik-kompakt
  - /museum/didaktik-m
  - /museum/microdigital-tk-95
  - /museum/robik
  - /museum/spica-ines
  oc_id: 945
  source:
    url: https://web.archive.org/web/20230618221029/http://www.old-computers.com/museum/computer.asp?c=945
    date: '2023-06-18'
---

The TK90X was the first [Sinclair Spectrum](/museum/sinclair-zx-spectrum/) clone produced by Microdigital. At the time, a special Brazilian regulation allowed local industry to produce and sell copies of foreign computers only to domestic market, however Microdigital computers were also sold in several south American countries.

Despite the case was quite the same as the original Spectrum, the TK90 wasn't fully compatible with it because of some additions to the software in ROM (User Defined Graphics editor, TRACE function, error messages in portuguese), and also some differences in I/O ports configuration and addresses. As a result a few games couldn't run on the TK90X, and some Sinclair peripherals could not be used.

The TK90X met a large success in Brazil thanks to a vast amount of pirated copies of Spectrum games available in the country.

Microdigital announced a **Microdrive clone** but it was never released. However, four other small companies (C.A.S., C.B.I., Syncron and Arcadia) released floppy disk drive interfaces. All interfaces were BetaDisk compatible. Except for the C.A.S. interface, all models had a built-in parallel printer interface.\
Other famous and very popular peripheral was the **Multiface 1** interface. Most brazillian M1's were produced by C.A.S.

One year later, Microdigital launched an improved version, the [TK-95](/museum/microdigital-tk-95/)

---

**Martin Revert** reports to us:\
In Argentina, it was possible to contact "pirate reverse engineers" who sold games adapted for the TK-90. They knew the Z80 assembler very well and also had a map with the ROM differences between the Spectrum and TK-90.\
I bought some games that worked fine in original Spectrum but not in TK-90. One example was Batman from the Ocean company. 3 weeks after the official release I've got the TK version running smoothly.\
I heard from them that the major problem was a NMI (Non Maskable Interruption). Aparently that thing was liberated in TK-90 and not in the Spectrum.\
The proliferation of Spectrum software piracy in South America have two explanations: The lack of distribution of official games and the strong presence of the Commodore 64 in the market.

Thanks to **Sebastian Rho** for all the pictures.

<table> <tr> <td></td> <td>We need more info about this computer ! If you designed, used, or have more info about this system, please send us pictures or anything you might find useful.</td> <td></td> </tr> </table>