TK 90X
Encyclopedia
Brazil
Brazil , officially the Federative Republic of Brazil , is the largest country in South America. It is the world's fifth largest country, both by geographical area and by population with over 192 million people...
ian ZX Spectrum
ZX Spectrum
The ZX Spectrum is an 8-bit personal home computer released in the United Kingdom in 1982 by Sinclair Research Ltd...
clone made in 1985 by Microdigital Eletronica
Microdigital Eletronica
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 , its first product was the TK80, a clone of the British microcomputer Sinclair ZX80.The company...
, a company located at São Paulo
São Paulo
São Paulo is the largest city in Brazil, the largest city in the southern hemisphere and South America, and the world's seventh largest city by population. The metropolis is anchor to the São Paulo metropolitan area, ranked as the second-most populous metropolitan area in the Americas and among...
, Brazil, that manufactured some ZX81
Sinclair ZX81
The ZX81 was a home computer produced by Sinclair Research and manufactured in Scotland by Timex Corporation. It was launched in the United Kingdom in March 1981 as the successor to Sinclair's ZX80 and was designed to be a low-cost introduction to home computing for the general public...
clones before (TK 82C
TK 82C
TK 82C was a Sinclair ZX81 clone made by Microdigital Eletrônica Ltda., a computer company located in Brazil.-General information:The TK 82C had the ZILOG Z80A processor running at 3.25 MHz, 2 KB SRAM and 8 KB of EPROM with the BASIC interpreter. The keyboard was made of layers of...
, TK 83 and TK 85
TK 85
The TK 85 was a ZX81 clone made by Microdigital Eletronica, a computer company located in Brazil. It came with 16 or 48 kB RAM, and had a ZX Spectrum-style case, more precisely a Timex Sinclair 1500 clone....
) and a ZX80
Sinclair ZX80
The Sinclair ZX80 is a home computer brought to market in 1980 by Science of Cambridge Ltd. . It is notable for being the first computer available in the United Kingdom for less than a hundred pounds...
clones (TK 80, TK 82).
The case was almost the same of the original Spectrum (just a little higher), and the keyboard placement was equal to the original keyboard, except for some additional commands that did not exist in the Spectrums (for characters defined by the user - UDG
UDG
- Universities :* University of Girona, a university located in the city of Girona, Spain.* University of Granma, a university located in Bayamo, Cuba.* University of Guadalajara, a university located in the city of Guadalajara, Mexico...
exactly in the place of 'Pound' symbol, and the 'Trace' function in Basic), and included specific Portuguese and Spanish characters such as ç and ñ, as well as accented vowels.
There were two versions: 16 Kb
Kilobyte
The kilobyte is a multiple of the unit byte for digital information. Although the prefix kilo- means 1000, the term kilobyte and symbol KB have historically been used to refer to either 1024 bytes or 1000 bytes, dependent upon context, in the fields of computer science and information...
and 48 Kb of RAM. Inside, the same processor: Z80A
Zilog Z80
The Zilog Z80 is an 8-bit microprocessor designed by Zilog and sold from July 1976 onwards. It was widely used both in desktop and embedded computer designs as well as for military purposes...
running at 3.58 MHz, a ROM
Read-only memory
Read-only memory is a class of storage medium used in computers and other electronic devices. Data stored in ROM cannot be modified, or can be modified only slowly or with difficulty, so it is mainly used to distribute firmware .In its strictest sense, ROM refers only...
chip, some RAM
Ram
-Animals:*Ram, an uncastrated male sheep*Ram cichlid, a species of freshwater fish endemic to Colombia and Venezuela-Military:*Battering ram*Ramming, a military tactic in which one vehicle runs into another...
chips (old dynamic RAMs 4116 and 4416). Microdigital did some reverse engineering to develop a CMOS
CMOS
Complementary metal–oxide–semiconductor is a technology for constructing integrated circuits. CMOS technology is used in microprocessors, microcontrollers, static RAM, and other digital logic circuits...
integrated circuit (IC) with similar functionality to the original Bipolar
Bipolar
-Medicine:* Bipolar cell* Bipolar cell of the retina* Bipolar disorder** Bipolar I disorder** Bipolar II disorder** Bipolar NOS* Bipolar spectrum-Astronomy:* Bipolar nebula, a two-lobed, axially symmetric nebula...
IC ULA from Sinclair/Ferranti. The modulator was tuned to VHF channel 3 and the TV system was hardware selectable to PAL-M (60 Hz) as used in Brazil, PAL-N (50 Hz) as used in Uruguay, Argentina and Paraguay and NTSC
NTSC
NTSC, named for the National Television System Committee, is the analog television system that is used in most of North America, most of South America , Burma, South Korea, Taiwan, Japan, the Philippines, and some Pacific island nations and territories .Most countries using the NTSC standard, as...
(60 Hz) as used in USA and many other countries, versatility of features the ZX Spectrum never had ** (Was discover an original ZX Spectrum with NTSC video output in Chile, The ULA is a model 6C011E-3 which generates a NTSC frame size and rate)
Another improvement over the original ZX Spectrum was the sound ouput via modulated RF direct to the TV set instead of the beeper.
Most of the software written for the Spectrum could be run on the TK 90X, but some minor incompatibilities occurred. Only three peripherals were released by Microdigital — a Joystick, a light pen interface and a parallel printer interface.
But a Beta disc(48) interface was make by many third party companies called 'C.A.S. disk drive interface' (almost an exact clone from the original Beta disc interface), 'C.B.I. disk drive interface' (with a printer interface included) and 'IDS91' (with a printer interface included made by Synchron) or 'IDS2001ne' (these exclusively compatible only with the TK90X or TK95{no ZX Spectrum use possible},also from Synchron) (and also with a printer interface included) .
The TK 90X was replaced by the TK 95
TK 95
The TK 95 microcomputer was the evolution of TK 90X made in the 1980s by Microdigital Eletronica, a company located at São Paulo, Brazil that manufactured some ZX81 clones before and a ZX80 clone...
, which had a different keyboard ( professional) and case (identical to Commodore Plus4), not in the rubber format, and exactly the same circuit board and schematics (even marked as TK90X on board, just a few difference in the ROM that made the TK95 more compatible with the original ZX Spectrum). But the same ULA chip, that have only digital logic ports with all the analogic part outside the ULA chip, exactly the same from TK90X. It have been reported that the TK95 had been providing more compatibility with the original ZX Spectrum (i.e. the game Mikie runs only on TK 95, not on TK 90X), but that was reported as a little change in the circuit board (the D1 diode has been disconnected, that made an improvement in ZX Spectrum compatibility) and the changes in the ROM from the TK95. Curiously, some games (fewer) became incompatible due to this modification. TK90X users in Brazil used to make a selectable switch to choose the original TK90X (or TK95) ROM or the ZX Spectrum ROM internally, so they could use almost all ZX Spectrum software.
During that period Brazilians were not allowed to import computers, and therefore the TK 90X became the first affordable color computer of Brazilians and was a big success. Similar status, because it was designed for Portuguese and Spanish language users, was achieved in other Latin America countries, as it was very successfully exported to Uruguay through its local distributor, Ingeniería de Sistemas (but the TK90X exported to these countries were a complete different circuit board and schematics, it also uses an original Ferrati ULA form ZX Spectrum, only externally was identical), and also to Argentina, Chile and Ecuador, where it competed with the Sinclair ZX Spectrum.
Because of its affordability, many commercial software programs were locally developed for the first time for use of small businesses in Latin America to run on the TK 90X, and millions of users had their first computer experience with it.