OSI300

(Image courtesy of EarlyComputers.com)

Model 300 Trainer ~1976

Single board trainer computer. Using 6502 CPU and 6810 128x8 Static RAM. There are switches and indicators for 8 data lines and 7 address lines, as well as swiches for RUN, RESET, LOAD, NMI and ROM.

Model 430 / Model 430B © 1977 Cassette & Analog I/O

Can be populated for Kansas City Standard Cassette Interface or for RS-232.
Cassette 300 to 1200 baud, RS-232 or current loop max 50K baud.
Has 8 parallel I/O lines, 2 fast D/A converters, and fast tracking A/D converter with 8 channel multiplexer. 

Uses S1883 UART for serial I/O
D/A - two 8bit 2v output 300ns settling time MC1408L8 chip
A/D - 8bit -1 to +1v one conversion per system cycle, usable with signals up to 20 KHz bandwidth. 1408L8 8-channel multiplexor National 3705
8 parallel I/O - 8 TTL latched outputs, 3 used by multiplexor,
8 TTL inputs, non-latched

Normally located @ $FB0x. Decodes 3 lowest adddress bits

Model 440B Video board

The OSI 440 video graphics board is a versitile high performance computer to TV interface. It can be economically populated as a terminal providing up to 32x32 characters on a screen and a keyboard input port. It can maximally be populated for 32x32 characters, 128x128 graphics and 4 color alphabetics.

Video: - 2V p-p into hi-Z, composite or ttl sync 60hz, 15.450Khz
Font: 5x7 uppercase ASCII
Format: 32 rows x 32 columns, unmodified TV sets typically display 24 x 24.
Keyboard input: 7 bit parallel ASCII with continuous strobe of at least 50us long-pulsed strobe
RAM: 1K x 6bit default
Graphics option: requires 446 kit, 420 memory board, (additional parts)
Address: Normally jumpered for $D000
Color output: uses upper 2 bits of character to select character color. white=0, red=1,green=2,yellow=3

OSI440B schematics

Model 470 disk controller board(same as Model 471)
Uses 6850 ACIA & 6520 PIA
Can optionally be configured as printer parallel I/O card

OSI470 floppy schematics   OSI470 printer I/O schematics
 

Works with OSI 65A serial PROM monitor, 65V video PROM monitor, and floppy disk bootstrap PROMs
Used in OSI C2P systems with OSI540A monochrome graphics adapter.

OSI500 schematics 

Used in OSI C4P and C8P systems
(This 502 board has the C2E ROM Monitor mods which map a 2K EPROM into $F800-$FFFF except for serial I/O at $FC00.)

OSI502 schematics

505B has I/O at $C704-C70E for connection to A15 I/O board which contains connectors for keypads, joystick, buffered I/O contains A0-A3, ø2, R/W, D0-D7 for Head End Cards. (MDS-since it requires external hardware, without hardware installed, looks like NULLREAD space I think...)
Uses disk I/O connector board A-13
Case uses port I/O connector board A-15
505B Used in OSI C4PMF systems

OSI505B schematics

Model 510 Triple CPU Board (6502, Z80, 6800) © 1979


3 CPUs: 6502A, 6800, Z-80, ACIA, PIA, 3 1702A PROMS for 6502 (256x8), 1 1702A PROM for 6800
Address decoding for up to 1MB memory
6502 Proms at $FDxx, $FExx, $FFxx
6800 Prom at $FFxx
Processor selection manual or connected to PIA PA6, PA7 (01 = Z80, 10=6800, 11=6502)
PIA PA0-PA3 -> A16 -A19.PA4 ->ROM/RAM sel, PA5->Processor Switch
Also configured as 2 CPU system board with 6502A & Z-80-4, 68B50, 6821, 6810 & 2716 DMon EPROM labeled OSI CP-1

OSI510 schematics

Model 520 RevB 16K RAM board © 1977
Model 520 RevC 16K RAM board © 1980

Uses 32 4Kx1 EMM 4200 /GTE 4300 22-pin static RAMs (3 voltages, +5, +12, -9) fully populated to 16K RAM

OSI520 schematics

Model 540 Rev A video board

Supports 32x32, and 64x32 video modes B&W, with 542 polled keyboard interface socket Character memory $D000-D7FF each display row always $40 bytes long Can be populated with 6bit of memory for 64 uppercase characters, or 8bit for full OSI character set. Contains KCS cassette interface for serial <-> cassette conversion.

OSI540A and 542A schematics

Model 540B video board © 1978

Supports 32x32, and 64x32 video modes with color, 542 keyboard interface socket Character memory $D000-D7FF each display row always $40 bytes long Color memory $E000-E7FF 4bits.
bit 0: 0= normal(bright txt, color background), 1= inverse(dark txt, bright background)
bit 1-3: 0=yellow, red, green, olive, blue, purple, sky blue, black

Write Register @ $DE00 controls video modes:
bit 0 1=32, 0=64
bit 1 1=tone on (542 keyboard)
bit 2 1=color on
bit 3 1=enable 38-40Khz AC Home control output

Read Register @ $DE00
bit 7 = video timing counter bit, 0 for 1/120 second, 1 for 1/120 second, based on video clock (60Hz)

OSI540B schematics

Model 542 and Model 542B Polled Keyboard

Usually connect through 540 Video board at $DFxx
Original Model 542 polled keyboard contains 8x8 keyboard matrix interface only. No tone, DAC noise outputs, or A15 connector.

Model 542B contains A15 connector for I/O board, 8x8 keyboard matrix, 8bit resistor ladder D/A conversion "noise" output, 8bit "tone" output.
 
Keyboard write @ $DF00 sets row, read at $DF00 read columns. A bit is set when a key is pressed. This is the opposite of the OSI 600 board keyboard.
Tone enable when bit 1 (0x02) is set at $DE00
Tone generator: frequency out = 49152/I where I = value stored at $DF01
DAC: Capacitively coupled output from R2R resistor DAC of value stored @ $DF01

OSI542B schematics

Model 555 Multi I/O expansion & RAM © 1979

"Jungle Board" Contains up to five 6850 style ACIA and two 6821 PIA Has space for up to 8K of 2114 RAM Provides parallel & serial I/O capabilities for printers, timeshare terminals, console & network interface.

4K RAM $D000
4K RAM $E000
4 RS-232 port $CExx
1 network node interface
NEC compatible interface
Centronics compatible interface

OSI555 schematics

Model 560Z CPU expander © 1977

Supports Z80 CPU and IM-600 (PDP-8 compatible) microprocessors plus three-way bus switching and run/single step circuitry. The 560Z runs under the command of a 6502 based 400, 500, or 510 system. Can support 64K of memory & I/O, but occupies only 4K of 6502 memory through a "sliding port-hole"

OSI560Z schematics