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IBM 7090/94 Console Operation

The 7090/94 series, like almost all large scale computers of its generation, had a large control console (IBM model 7151) that was used to run programs; monitor and control the overall status of the machine; and, occasionally, to manually debug software.

Jobs were almost always run on a closed shop basis whereby users would submit card decks and then wait anywhere from several hours to several days for the printed results.

The console displayed the current status of the most important machine registers (via small incandescent lights -- one for each bit) and also allowed the operator/programmer to modify, on the fly, various registers and machine control variables by flipping switches etc. Complete programs, written in binary, could be directly entered through the control console. This obviously laborious and slow method could be used to build boot strap loaders, simple maintenance and test programs, and the like (considering the typical cost of the machine -- approximately $100/hour (perhaps $750 in 2001 dollars), this method was used as little as possible). Self-loading magnetic tapes, prepared on a separate less expensive machine, could be mounted and the contents automatically loaded into memory and executed -- which was the method typically employed for most user production programs by the operations staff with printed results written to output magnetic tapes.

The control console for the 7094 differed in minor respects from that used for the 7090 -- primarily in the addition of extra index register displays for the 7094 and an additional switch that would command the 7094 to operate as a 7090 with respect to multiple indexing. The additional index registers on the 7094 were displayed on a small vertical panel mounted on top of the console unit.

Press to see a high-resolution photograph (950kb) of the 7094 console where all of the above described items may be seen in detail.

Console Controls and Indicators
Register Displays (Lights):Multiplier/Quotient ('M/Q')36-Bits
'Accumulator' (AC)38-Bits
Index Registers ('Index A'-'Index G' for 7094, 'Index A' -'Index C' for 7090)15-Bits Each
'Instruction Counter'15-Bits
'Instruction Register'18-Bits (Sign Bit-9 were for Op. Code and 10-17 were the Shift Counter)
Indicators:When ON, Indicated...
'Trap'Computer in 'Transfer Trap' Mode
'Simulate'7090/94 was in '704/709 Mode'
'Accumulator Overflow'Overflow in AC
'Quotient Overflow'Overflow in MQ
'Read/Write Select'I/O Unit Selected
'Divide Check'Divide Check Error
'Sense Lights'Sense Lights being Set by Program
'Trap Control'Channel was Not Executing a Trap
Channel Indicators:When ON, Indicated...
'Channel Select'Channel in Operation
'Channel Trap'Channel was Enabled to Trap
'Tape Check Trap'Channel was Enabled for Tape Check
'Channel Tape Check'Tape Error
Lighted Buttons (Used to Indicate Certain Conditions):When ON, Indicated...
'I/O Check' (White)I/O Channel Error
'Ready' (White)Computer Power was OK
'Automatic' (Yellow)Automatic Mode or Data Channel in Operation
'Console Power On' (Red)Power Applied to Console
'I/O Power Check' (Yellow)Fuse Out in I/O
'Power' (Red)Power ON in Entire System
Panel Keys and Switches (Used to Start the Computer, Load Programs, etc.):Purpose:
'Auto-Manual' SwitchStopped Computer after Completion of Current Instruction or I/O
'Clear' KeyIn Automatic Mode, Zeroed all Core Memory
'Reset' KeySet all Registers except SI to Zero and Turned Off all Indicators
'Display Indicators' KeyDisplayed Sense Indicators in Storage Register
'Display Effective Address' KeyIndexed Address Shown in SR (Manual Mode)
'Load' KeyInitiated Loading of Self-Loading Binary Tape
'Start' KeyContinued with Program
'Single Step' and 'Multiple Step' KeysStepped through Program
'Enter MQ' KeyPut Keyed-In Word into MQ Register
'Enter Instruction' KeyExecuted Instruction in Panel Entry Keys (Manual Mode)
'Display Storage' KeyDisplayed Storage Location Referenced by Panel Entry Keys
'Sense' SwitchesManual Switches to be Interrogated by Program
Panel Input Switches36 Switches to Insert a Word of Information into the MQ or Instruction Register
'Reset' SwitchReset all Panel Switches to Off or Zero
'Emergency Power Off' SwitchFor Emergency Only -- Last Revision: 23 August 2001
Copyright © 1996 - 2017 Jack Harper (unless otherwise noted)
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