File:Osborne 4 Theory of Operation Manual Rev 1.0 1985.pdf

Osborne 4 Theory of Operation Manual, Revision 1.0, Osborne Computer Corporation Technical Publications, part number 2F40006-01, August 1985. 81 scanned pages, no text layer. It describes the two boards of the Osborne 4 (Osborne Vixen) and corresponds to the revision C schematics: system timing from the 23.9616 MHz oscillator, the Z80A CPU, reset and interrupt logic, I/O decoding, the single 2732 monitor ROM at 4C, the eight 4164 dynamic RAMs, keyboard control through the system-board 8155, the I/O board (8155 parallel port programmable as IEEE-488 or Centronics, 8251A serial port, RS-232-C), the 1797 floppy disk controller with a diskette capacity table (Table 9-1), and the display controller. It contains no parts list, no power supply or monitor information and no fault-finding procedures. Described on Osborne 4 Theory of Operation Manual.

https://archive.org/details/osborne-4-cbios-rev-1-01 (item "Osborne Vixen Technical Reference Manual", uploaded by [email protected]), file "Osborne 4 Theory of Operation Manual Revision 1_0 Corresponds to Revision C Schematics.pdf" (retrieved 2026-10-01)

Osborne Computer Corporation, Fremont, California.

Copyright 1985 Osborne Computer Corporation. Hosted for preservation and repair reference.