DA28-F

This document is an Engineering Change Order Log (DEC-O-LOG) from Digital Equipment Corporation, detailing updates for the DA28-F Interprocessor Buffer, which connects PDP-11 systems to a Positive Bus and is used with DECsystem-10 and PDP-11 processors.

It describes two major engineering changes:

1. DA28F-B0001 (September 1973): Addressed seven problems, including issues with CONNECT/COMMON REQUEST signals, JAM switch misconfiguration, unreliable JAM operation, WCOF signal causing software bugs, and incorrect processor synchronization. The solution involved significant hardware modifications, such as adding M133 and M246 modules, a resistor, and extensive wiring changes (81 additions, 47 deletions). This change required 9.0 hours to install.

2. DA28F-B0002 (January 1974): Primarily corrected unreliable "JAM" option operation specifically with PDP-11/40 or PDP-11/45 CPUs through detailed wiring changes. It also fixed print errors in the documentation. This change required 1.8 hours to install.

Both changes were mandated for retrofit on all existing DA28-F units, both in manufacturing (in-plant) and in the field.