MSX is a standardized home computer architecture, announced by Microsoft and ASCII Corporation on June 16, 1983. It was initially conceived by Microsoft as a product for the Eastern sector, and jointly marketed by Kazuhiko Nishi, then vice-president at Microsoft and director at ASCII Corporation. Microsoft and Nishi conceived the project as an attempt to create unified standards among various home computing system manufacturers of the period, in the same fashion as the VHS standard for home video tape machines.
MSX systems were popular in Japan and several other countries. Sony was the primary manufacturer of MSX systems at the time of release, and throughout most of the products’ lifespan, producing more units than any other manufacturer. Eventually 5 million MSX-based units were sold in Japan alone. Despite Microsoft’s involvement, few MSX-based machines were released in the United States.
The meaning of the acronym MSX remains a matter of debate. In 2001, Kazuhiko Nishi recalled that many assumed that it was derived from “Microsoft Extended”, referring to the built-in Microsoft Extended BASIC (MSX BASIC). Others believed that it stood for "Matsushita-Sony". He said that the team’s original definition was "Machines with Software eXchangeability". This seems plausible, although, in 1985, he gave a conflicting definition, that he named MSX after the MX missile.
Before the success of Nintendo’s Family Computer, MSX was the platform for which major Japanese game studios such as Konami and Hudson Soft produced video games. The Metal Gear series, for example, was first written for MSX hardware.
The MSXVR is a computer released in 2020 and compatible with the MSX family of computers. Like the latest Zenmix game consoles, it is also based on a Raspberri Pi card with additional circuitry to connect the original MSX peripherals.
|Release||Worldwide (1983)||Worldwide (1985)||Only officially in Japan (available in Europe and Brazil via upgrades) (1988)||Only Japan (1990)|
|Processor||Zilog Z80A running at 3.58 MHz||Zilog Z80A running at 3.58 MHz||Zilog Z80-compatible running at 3.58 MHz (the MSX2+ models from Panasonic can be se|
The keyboard is a functionally separate unit which could be connected by non-multiplexed and multiplexed interfaces. Multiplexed keyboard units feature additional data direction line, allowing sending scan line number to the keyboard using same data lines used for return scan code, decreasing overall number of wires between keyboard and machine. Non-multiplexed interface is usually used for internal keyboards (and some external keyboards, like Panasonic CF-3300); multiplexed interface is used for external keyboards (e.g. in Yamaha YIS805 model).
The keyboard is organized as a matrix with maximum 11 input lines and 8 output lines, accounting for maximum 88 keys (including all control, numerical and alphanumerical keys). Each scan line is regularly queried to identify the state of the keys on the line; query speed is identified by the system interrupt frequency. Such organization allows system to sense state of each key, not exhibiting notorious problem with 8042 microcontroller-based keyboards when pressing several keys simultaneously (usually more than 3) generates wrong input characters, or renders inability to sense the press of more keys.
Due to the keyboard scan being controlled by the system interrupts, one of the troubleshooting hints when an MSX machine does not display any image (assuming power is present) is to press the CAPS key to see if the respective LED toggles. If it does not toggle, the system is likely suffering a more serious problem than just lack of image on the screen (i.e. the problem with video cable or video display interface in overall).
In 2009 Kamil Karimov designed the adapter board to connect PS/2 keyboard to the multiplexed MSX keyboard interface. The firmware embedded into its ATTiny chip was tailored for Daewoo CPC machines.
In 2011 AGE Labs embedded a PS/2 keyboard controller unit, based on Microchip microcontroller, into its GR8BIT do-it-yourself machine. Its firmware is developed to directly convert PS/2 scan codes to the MSX keyboard scan codes. Thus it is fully transparent to the applications, allowing use of the controller unit with different MSX-compatible machines and for different localization setups.
MSX standard requires at least 1 cartridge slot, most MSX models have 2. These slots are interchangeable, so in most cases it makes no difference in which slot a cartridge is inserted. The physical connector is a 50 pin (2 x 25 contacts), standard 2.54 mm (0.1 inch) pitch edge connector. Using these cartridge slots, a wide variety of peripherals could be connected.
Regular game cartridges are about the size of an audio cassette (so-called "Konami size"). Despite their higher cost, this was a popular format due to its reliability and ease of use.
Around 1985, Hudson Soft released the credit card-sized Bee Card, which was meant as a cheaper and more convenient alternative to ROM cartridges. But it was a commercial failure, and very few titles were released on the format.
Floppy disk drives
MSX systems generally did not have a built-in disk drive, so games were published mainly on cartridge and cassette tape. Sony created a battery backed RAM cartridge the HBI-55 "data cartridge" for some computers in their "Hit-Bit" line of MSX systems, that could be used to store programs or data as an alternative to cassette tapes.
Floppy disk drives were available for MSX however, in the form of a cartridge containing the disk interface electronics and a BIOS extension ROM (the floppy disk drive interface), connected to an external case with the drive. In South-America, many of these systems used a 5.25 in (133 mm) floppy disk drive, but in Europe, 3.5 in (89 mm) drives were more popular. In Japan, some MSX1 systems included a built-in 3.5" disk drive, like the Panasonic (previously named Matsushita) CF-3000. In Europe, a range of Philips MSX2 systems NMS 8230, 8235, 8245, 8250 and above featured either 360 or 720 Kb 3.5" floppy drives.
In 1985, the MSX2 was released, and these systems often (but not always) included a built-in 3.5" disk drive too. Consequently the popular media for games and other software shifted to floppy disks.
The MSX-DOS disk operating system had internal software mechanisms much like CP/M (so CP/M software could be ported reasonably easily), but had a file system compatible with MS-DOS. Its user commands were also similar to early MS-DOS versions. In this way, Microsoft could promote MSX for home use while promoting MS-DOS based personal computers in office environments.
The MSX 3.5" floppy disks are directly compatible with MS-DOS (although some details like file undeletion and boot sector code were different). Like MS-DOS 1, MSX disks (formatted) under MSX-DOS 1 have no support for subdirectories.
In September 2012, AGE Labs extended the standard by including support for 1.44Mb 3.5” format. The 1.44Mb diskette size goes in two configurations: Standard (1 sector per cluster, 9 FAT sectors), and Compatible (4 sectors per cluster, 3 FAT sectors).