Peripherals are connected to the 9845 mainframe via so-called interface modules. Interface modules are responsible for translating between the system I/O bus (the IOD bus) and the peripheral interface. Just like the expansion boards of a modern PC they plug into the system I/O bus via edge connectors, from where they are connected to the data and control lines of the IOD bus as well as to the power supply. In contrast to PCs, the modules are not installed inside the mainframe, but can be easily plugged in and removed at the rear of the mainframe without the need to open it.


Each interface module consists of one or two PCBs inside of a standardized pastic housing which can be fixed into the slot with a snap-in machanism. In order to distinguish the interface modules, each interface module has a switch, through which it can be assigned a unique ID, the selection code. All interface modules connect to the peripheral via a suitable cable and connector (in fact, those interfaces look much more like cables than like expansion boards). Actually, there is one interface module, the Real Time Clock module, which doesn't necessarily connect to a peripheral device. Some of the interface modules are really complex devices, for example the 98046B datacomm interface is a small computer with its own 8048 microcontroller.

  Product No. Option Description   Retail
98029A 98029A   Resource Management Interface (for the 9845B/C, with integrated Z80 microcontroller). Resource Management ROM required.    
98032A 98032A   16-Bit Parallel I/O (GPIO). Development code name "Parsley".   $525
    445 Open Ended Cable    
    040 Multiprogrammer    
    062 9862A Plotter    
    063 9863A Paper Tape Reader    
    064 9864A Digitizer    
    066 9866A/B Thermal Printer    
    069 9869A Card Reader    
    071 9871A Impact Line Printer    
    081 9881A Printer    
    083 9883A Paper Tape Reader    
    084 9884A Paper Tape Punch    
    085 9885A Flexible Disk    
98033A 98033A 445 BCD Input Interface. Development code name "Sage", provided with open ended cable.   $525
98034B 98034A/B 445 HP-IB Interface Bus. I/O ROM required. Development code name "Rosemary". Provided with standard metric connector.   $600
98035A 98035A  

Real Time Clock Interface.

IMPORTANT NOTE: If you're going to acquire one of those, immediately replace the internal NiCd accumulator before plugging the interface into the 9845 backplane (2.4V substitutes should be easy to find). Those batteries use to leak, thereby spoiling the PCBs. Double-check the polarity. I recommend to solder in sockets for easy plug-in and later replacements.

Development code name "Thyme".

    001 U.S. Date Format    
    002 European Date Format    
    100 RTC With Unterminated I/O Cable    
98036A 98036A   RS-232C Interface (with DTE Cable for terminal connection). I/O ROM recommended. Development code name "Cap'n Crunch".   $735
    001 DCE Cable (for modem connection)    
    002 Special Cable for Distributed Systems Software    
  98037A   A/D Interface (never sold). Development code name "Prism".    
  98040A 445 Incremental Plotter Interface. Provided with Canon SK-19-212C-1/2 connector.   $630
98041A 98041A 045 Disk Interface (no disk cable provided).   $3,000
98046B 98046A/B   RS-232C Data Communications Interface (with integrated 8048 microcomputer and DTE Cable for terminal connection). Bisync Datacomm ROM required.   $950
    001 DCE Cable (for modem connection)    

For some interfaces, test connectors for hardware verfication were available:

Product No. Description   Retail
98241-67932 Test connector for 98032A   $160
98241-67933 Test connector for 98033A   $45
98241-67936 Test connector for 98036A   $26

All development code names on this page go back to Joe Rigdon's HP 98x5 Series Interface web page.