The Gigatron TTL is a

retro-style Retro style is imitative or consciously derivative of lifestyles, trends, or art forms from history, including in music, modes, fashions, or attitudes. In popular culture, the " nostalgia cycle" is typically for the two decades that begin 20–3 ...

8-bit In computer architecture, 8-bit Integer (computer science), integers or other Data (computing), data units are those that are 8 bits wide (1 octet (computing), octet). Also, 8-bit central processing unit (CPU) and arithmetic logic unit (ALU) arc ...

computer A computer is a machine that can be programmed to Execution (computing), carry out sequences of arithmetic or logical operations (computation) automatically. Modern digital electronic computers can perform generic sets of operations known as C ...

, where the

CPU A central processing unit (CPU), also called a central processor, main processor or just processor, is the electronic circuitry that executes instructions comprising a computer program. The CPU performs basic arithmetic, logic, controlling, and ...

is implemented by a set of TTL chips instead of a single

microprocessor A microprocessor is a computer processor where the data processing logic and control is included on a single integrated circuit, or a small number of integrated circuits. The microprocessor contains the arithmetic, logic, and control circu ...

, imitating the hardware present in early arcades. Its target is the computing enthusiasts, for studying or hobby purposes. Gigatron TTL Microcomputer

Architecture

The CPU is implemented through a small set of TTL 7400 series chips, running at 6.25

MHz The hertz (symbol: Hz) is the unit of frequency in the International System of Units (SI), equivalent to one event (or cycle) per second. The hertz is an SI derived unit whose expression in terms of SI base units is s−1, meaning that one he ...

base

clock rate In computing, the clock rate or clock speed typically refers to the frequency at which the clock generator of a processor can generate pulses, which are used to synchronize the operations of its components, and is used as an indicator of the pr ...

, that can be overclocked by providing better chips. RAM can also be increased in the same way. Three CPU modes are implemented: *

native assembly code, that implements a

Harvard architecture The Harvard architecture is a computer architecture with separate storage and signal pathways for instructions and data. It contrasts with the von Neumann architecture, where program instructions and data share the same memory and pathways. ...

. This mode offers a 17

instruction set In computer science, an instruction set architecture (ISA), also called computer architecture, is an abstract model of a computer. A device that executes instructions described by that ISA, such as a central processing unit (CPU), is called an ' ...

, and supports up to 256 instructions: 8 ALU operations, 8

addressing mode Addressing modes are an aspect of the instruction set architecture in most central processing unit (CPU) designs. The various addressing modes that are defined in a given instruction set architecture define how the machine language instructions in ...

s and 4 bus modes. The ROM firmware and the vCPU interpreter are written in the 8-bit Native assembly code. *16-bit vCPU interpreter, that implements a

von Neumann architecture The von Neumann architecture — also known as the von Neumann model or Princeton architecture — is a computer architecture based on a 1945 description by John von Neumann, and by others, in the ''First Draft of a Report on the EDVAC''. The ...

and has a 34 instructions set. It loads and runs programs from the

RAM Ram, ram, or RAM may refer to: Animals * A male sheep * Ram cichlid, a freshwater tropical fish People * Ram (given name) * Ram (surname) * Ram (director) (Ramsubramaniam), an Indian Tamil film director * RAM (musician) (born 1974), Dutch * Ra ...

. The integrated programs are written for this vCPU. *

MOS 6502 The MOS Technology 6502 (typically pronounced "sixty-five-oh-two" or "six-five-oh-two") William Mensch and the moderator both pronounce the 6502 microprocessor as ''"sixty-five-oh-two"''. is an 8-bit microprocessor that was designed by a small te ...

emulator (experimental), able to run MOS 6502

machine code In computer programming, machine code is any low-level programming language, consisting of machine language instructions, which are used to control a computer's central processing unit (CPU). Each instruction causes the CPU to perform a very ...

. The

video Video is an electronic medium for the recording, copying, playback, broadcasting, and display of moving visual media. Video was first developed for mechanical television systems, which were quickly replaced by cathode-ray tube (CRT) syste ...

is generated by the ROM firmware (native assembly code), and supports a

resolution Resolution(s) may refer to: Common meanings * Resolution (debate), the statement which is debated in policy debate * Resolution (law), a written motion adopted by a deliberative body * New Year's resolution, a commitment that an individual mak ...

of 160x120 pixels with 64 colours stored in RAM starting at address 0x0800 and ending at 0x7F9F as 120 segments of 160 bytes of non-contiguous RAM. Pixels are stored as 1 byte per pixel in XXBBGGRR format, (the top 2 bits are unused and may be used by the programmer for their own usage). The video display contains a configurable number of black (empty) scanlines in order to save vCPU time for programs; these empty/black scanlines can be configured by the user to get more displayed raster scanlines or more vCPU time for user programs. Off-screen RAM begins at 0x08A0 and ends at 0x7FFF as 120 segments of 96 bytes of non-contiguous RAM; these fragmented sections of RAM may be used for storing data or code or for scrolling effects using the video indirection table. System RAM is trivially expandable from the default 32K bytes to the full 16bit addressable size of 64Kbytes. The audio is also generated by the ROM firmware during horizontal blanking periods, providing four 6 bit

channels Channel, channels, channeling, etc., may refer to: Geography * Channel (geography), in physical geography, a landform consisting of the outline (banks) of the path of a narrow body of water. Australia * Channel Country, region of outback Austral ...

, (software mixed and output at 4 bit PCM), with 4 selectable and user-modifiable 64-byte waveforms stored in RAM, (re-generated at Cold Boot and for ROMv4 and above on all reboots), and providing simple amplitude and XOR modulation per channel.

Software

The programs are included in the ROM chip, and these are written in GCL (Gigatron Control Language), BASIC or vCPU. The following programs are included: *Snake, a simple version of the

snake Snakes are elongated, Limbless vertebrate, limbless, carnivore, carnivorous reptiles of the suborder Serpentes . Like all other Squamata, squamates, snakes are ectothermic, amniote vertebrates covered in overlapping Scale (zoology), scales. Ma ...

graphical game *Racer, a ''

Pole Position In a motorsports race, the pole position is usually the best and "statistically the most advantageous" starting position on the track. The pole position is usually earned by the driver with the best qualifying times in the trials before the rac ...

''-like game *Mandelbrot, a

Mandelbrot set The Mandelbrot set () is the set of complex numbers c for which the function f_c(z)=z^2+c does not diverge to infinity when iterated from z=0, i.e., for which the sequence f_c(0), f_c(f_c(0)), etc., remains bounded in absolute value. This ...

image generator *Pictures, an

image viewer An image viewer or image browser is a computer program that can display stored graphical images; it can often handle various graphics file formats. Such software usually renders the image according to properties of the display such as color depth, ...

for the pre-loaded pictures *Tetronis, a

Tetris ''Tetris'' (russian: link=no, Тетрис) is a puzzle video game created by Soviet software engineer Alexey Pajitnov in 1984. It has been published by several companies for multiple platforms, most prominently during a dispute over the approp ...

clone *Bricks, a '' Breakout'' clone *TicTacToe, a text-mode

tic-tac-toe Tic-tac-toe (American English), noughts and crosses (Commonwealth English), or Xs and Os (Canadian or Irish English) is a paper-and-pencil game for two players who take turns marking the spaces in a three-by-three grid with ''X'' or ''O''. T ...

written in BASIC *BASIC, a

Tiny BASIC Tiny BASIC is a family of dialects of the BASIC programming language that can fit into 4 or fewer KBs of memory. Tiny BASIC was designed in response to the open letter published by Bill Gates complaining about users pirating Altair BASIC, which ...

interpreter *WozMon, a Woz Monitor rendition *Loader, a feature to load vCPU or

BASIC BASIC (Beginners' All-purpose Symbolic Instruction Code) is a family of general-purpose, high-level programming languages designed for ease of use. The original version was created by John G. Kemeny and Thomas E. Kurtz at Dartmouth College ...

programs over the joystick port *Credits, shows the credits in text that change colours The Tiny BASIC interpreter allows users to create programs, change the systems parameters, and load and save programs to the non-volatile memory in the built-in keyboard controller. The software included is licensed under the 2-clause BSD license.

Assembly kit

The microcomputer is sold as assembling kit, that includes: * A

PCB PCB may refer to: Science and technology * Polychlorinated biphenyl, an organic chlorine compound, now recognized as an environmental toxin and classified as a persistent organic pollutant * Printed circuit board, a board used in electronics * ...

. *

7400 series The 7400 series of integrated circuits (ICs) are a popular logic family of transistor–transistor logic (TTL) logic chips. In 1964, Texas Instruments introduced the SN5400 series of logic chips, in a ceramic semiconductor package. A low-co ...

TTL chips. * A swappable

EPROM An EPROM (rarely EROM), or erasable programmable read-only memory, is a type of programmable read-only memory (PROM) chip that retains its data when its power supply is switched off. Computer memory that can retrieve stored data after a power s ...

chip and a

socket Socket may refer to: Mechanics * Socket wrench, a type of wrench that uses separate, removable sockets to fit different sizes of nuts and bolts * Socket head screw, a screw (or bolt) with a cylindrical head containing a socket into which the hexag ...

(for firmware updates). *A 32 KB

CMOS Complementary metal–oxide–semiconductor (CMOS, pronounced "sea-moss", ) is a type of metal–oxide–semiconductor field-effect transistor (MOSFET) fabrication process that uses complementary and symmetrical pairs of p-type and n-type MOSFE ...

SRAM (upgradable to a 64 KB chip) *

Game controller A game controller, gaming controller, or simply controller, is an input device used with video games or entertainment systems to provide input to a video game, typically to control an object or character in the game. Before the seventh generation ...

and

VGA Video Graphics Array (VGA) is a video display controller and accompanying de facto graphics standard, first introduced with the IBM PS/2 line of computers in 1987, which became ubiquitous in the PC industry within three years. The term can now ...

(

D-SUB The D-subminiature or D-sub is a common type of electrical connector. They are named for their characteristic D-shaped metal shield. When they were introduced, D-subs were among the smallest connectors used on computer systems. Description, no ...

) ports. *

USB Universal Serial Bus (USB) is an industry standard that establishes specifications for cables, connectors and protocols for connection, communication and power supply (interfacing) between computers, peripherals and other computers. A broad v ...

port and cable for power. * A

game controller A game controller, gaming controller, or simply controller, is an input device used with video games or entertainment systems to provide input to a video game, typically to control an object or character in the game. Before the seventh generation ...

similar to the

NES The Nintendo Entertainment System (NES) is an 8-bit third-generation home video game console produced by Nintendo. It was first released in Japan in 1983 as the commonly known as the The NES, a redesigned version, was released in American ...

one. * A keyboard controller with built-in

non-volatile memory Non-volatile memory (NVM) or non-volatile storage is a type of computer memory that can retain stored information even after power is removed. In contrast, volatile memory needs constant power in order to retain data. Non-volatile memory typic ...

. * Resistors,

capacitor A capacitor is a device that stores electrical energy in an electric field by virtue of accumulating electric charges on two close surfaces insulated from each other. It is a passive electronic component with two terminals. The effect of ...

s and

diodes A diode is a two-terminal electronic component that conducts current primarily in one direction (asymmetric conductance); it has low (ideally zero) resistance in one direction, and high (ideally infinite) resistance in the other. A diode ...

. * A set of 4 customisable

LED A light-emitting diode (LED) is a semiconductor Electronics, device that Light#Light sources, emits light when Electric current, current flows through it. Electrons in the semiconductor recombine with electron holes, releasing energy i ...

s. * Instruction booklet. * A wooden box for presentation and assembling. The kit does not include a

keyboard Keyboard may refer to: Text input * Keyboard, part of a typewriter * Computer keyboard ** Keyboard layout, the software control of computer keyboards and their mapping ** Keyboard technology, computer keyboard hardware and firmware Music * Musi ...

nor

. A keyboard controller connectable to the game controller port is shipped with a small built-in non-volatile memory, for storing

programs. An

Arduino Arduino () is an open-source hardware and software company, project, and user community that designs and manufactures single-board microcontrollers and microcontroller kits for building digital devices. Its hardware products are licensed unde ...

board can be programmed for interacting between a

and the microcomputer, as for programming, as well as for additional storage.

Availability

The kit was available for purchase at €149.50. The updates were provided through a new ROM chip, shipped as an update, that should be changed manually. The original kits are no longer available due to the depletion of the stock and Marcel van Kervinck's death. However, a Dutch company is producing kits for €99.95. There is also an emulator available online, able to load precompiled vCPU and Tiny BASIC programs.

References

External links

* * * The 8-Bit Guy - * The 8-Bit Guy - * Dave Jones - * Ben Heck - * * * {{URL, https://hackaday.com/2019/07/02/emulating-a-6502-in-rom/, Hackaday - Emulating a 6502 in ROM Microcomputers Retro style Computer-related introductions in 2018