Usuario:Mcapdevila/Superboard

The Superboard II microcomputer (1978) was a single-board computer manufactured by Ohio Scientific,^[1] with a 24×24 pseudo-graphic display working at NTSC video frequencies. The video output was black and white with 256 characters generated by a two kilobyte ROM. It had no bit-mapped graphics capability. The video output could be fed to an external UHF modulator, if a connection to a TV set was desired.^[2]

Description

The Superboard II launching was advertised as the first Microsoft floating point ROM BASIC (ported from the RAM version), in Byte Magazine and Kilobaud Micro-computing, two hobbyists magazine of the time. The Superboard II was the least expensive computer, retailing for around the $279 price range, with an onboard BASIC programming language. It came without a case or power supply. It was a single board computer with the keyboard integrated on the same printed circuit board. It was shipped with 4KB of RAM (upgradable to 8KB), a 2KB BIOS in ROM (known as SYNMON as the ROM was labeled 'SYN600' or 'SYNMON 1.0') and the earliest version of Microsoft 8K BASIC. OSI 6502 BASIC Version 1.0 Revision 3.2 (c) 1977 By Microsoft.^[3]

The version OSI C1P / 600D Superboard II (occasionally advertised as the 'Colorboard') featured an unpopulated socket for an extra 1k × 4-bits of video RAM to hold character color information. The implementation of this was detailed in the OSI user group newsletter which was published around four times a year. The 600D also featured two video modes: 32×32 (~24×24 visible) for 'graphics', or 64×16 (~48×15 visible) for text where each text line had a blank line between it and the next.^[3]

The mode could be selected by a poke to the keyboard register. The computer couldn't write to the video memory without glitching the display. There was an add-on graphics card for the Superboard that would display 256 by 256 pixels. It came with software to draw 3D graphics.The keyboard polling register (a simple 8-bit TTL Latch) was also used as a very crude digital-to-analog converter by means of a resistor ladder connected to an 'audio out' socket to the right of the keyboard.

CPU

The Superboard II was powered by a 6502 microprocessor CPU running at 1 MHz, and was equipped with up to 8 kilobytes of RAM using 2114 static RAM chips of 1024×4-bit. An additional memory-mapped 1 KB of RAM was used for the video display. It had the 8K Microsoft BASIC interpreter stored in ROM. In addition to Basic, a 6502 machine code monitor (2Kb) was built into ROM. It allowed programming by entering sequences of 6502 operational codes. Later a two pass assembler was available which allowed the use of assembly language.

Although the 6502 has two interrupt input pins (NMI and IRQ), neither was used by the Superboard II.

Video

The Superboard II had a 16-row, 48-column memory-mapped video display. All scrolling and character output functions were handled by firmware. In the original ROMs, the output functions were rudimentary and did not include a clear-screen function. CPU access to video memory caused noticeable glitches (known as "snow") on the screen.

Cassette interface

In common with other home computers of the time, software could be saved and loaded on standard cassette tapes. The Superboard II used the Kansas City standard tape format. I/O was managed by a Motorola 6850 ACIA. This allowed a full RS-232 port to be implemented, with the addition of a few extra components and minor modifications to existing jumpers on the board.

Keyboard interface

The keyboard of the Superboard II was located on the main PCB, and comprised a matrix of keyswitches. The matrix was interfaced to the CPU via two 8-bit I/O ports, and was polled by firmware in the machine's ROMs. One key was a latching type, the shift-lock key. When supplied as a kit, the keyboard was assembled by the purchaser from a bag of switches and keytops.

The keyboard ports were located at address DF00 (hex), or 57088 (decimal). BASIC programs typically polled for real-time keyboard input by using the PEEK and POKE commands at that address. Because the keyboard lacked any way to generate an interrupt, it was not possible to typeahead. The keyboard matrix also lacked any diodes at the intersections of the matrix. This led to problems when reading certain combinations of keys pressed simultaneously. The matrix was designed to allow only the shift, control and shift-lock keys to be pressed simultaneously with another key.

Expansion sockets

The 40 pin expansion socket opened up the world to the Superboard II. One could attach a dual floppy disk controller (5.25") and a memory expansion card (40K max) to allow faster and reliable save/load of programs/data.

A sound card became available, built around the General Instrument AY-3-8910, which together with a peripheral interface Adaptor (PIA) chip - 6521, gave the Superboard II VOICE.

Notes

↑ Bonnier Corporation (May 1981). Popular Science. Bonnier Corporation. pp. 59-. ISSN 01617370.
↑ Hearst Magazines (August 1980). Popular Mechanics. Hearst Magazines. pp. 107-. ISSN 00324558.
↑ ^a ^b Bonnier Corporation (December 1978). Popular Science. Bonnier Corporation. pp. 104-. ISSN 01617370.

External links

II.htm Compukit Superboard II Home Page – At BeeJay's home page
Ian's Compukit Home Page
How to build a Superboard II
Kansas City Tape Decoder
II A collection of Superboard II software rescued from tapes

Categor:Early microcomputers Categor:6502-based home computers Categor:Home computers Categor:Products introduced in 1979

[Corporation1981-1] Bonnier Corporation (May 1981). Popular Science. Bonnier Corporation. pp. 59-. ISSN 01617370.

[Magazines1980-2] Hearst Magazines (August 1980). Popular Mechanics. Hearst Magazines. pp. 107-. ISSN 00324558.

[Corporation1978-3] Bonnier Corporation (December 1978). Popular Science. Bonnier Corporation. pp. 104-. ISSN 01617370.

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