The D-17B is a computer used in missile guidance systems, specifically the Minuteman I NS-1OQ missile guidance system, which contains a D-17B computer, the associated stable platform, and power supplies. The D-17B weighs approximately 62 pounds (28.1 kg), contains 1,521 transistors, 6,282 diodes, 1,116 capacitors, and 504 resistors. These components are mounted on double copper-clad, engraved, gold-plated, glass fiber laminate circuit boards. There are 75 of these circuit boards and each one has been coated with a flexible polyurethane compound for moisture and vibration protection. The high degree of reliability and ruggedness of the computer are evidenced by the strict requirements of the weapons system. Use of the D-17B is especially appropriate when high reliability is necessary under extreme environmental conditions such as high shock, acceleration, or vibration that preclude the use of other computers.

Since an airborne, computer-controlled missile only gets one chance to execute its mission, the design specifications of the D-17B required very high reliability. This was achieved by using DRL (diode-resistor) logic

Diode logic

Diode logic or diode-resistor logic constructs Boolean logic gates from diodes acting as electrically operated switches. While diode logic has the advantage of simplicity, the lack of an amplifying stage in each gate limits its application...

 extensively and only using DTL (diode-transistor) logic

Diode-transistor logic

Diode–transistor logic is a class of digital circuits that is the direct ancestor of transistor–transistor logic. It is called so because the logic gating function is performed by a diode network and the amplifying function is performed by a transistor .- Implementations :The DTL circuit shown in...

 where gain or inversion was required in this fully solid-state computer. In the early 1960s when the D-17B was designed, transistors were not as reliable as they are now, thus the designers used transistors only when necessary. The

Specifications

Minuteman I D-17B Computer Specifications

Year: 1962

The D17B is a synchronous serial general-purpose digital computer.

Manufacturer:
Autonetics Division of North American Aviation

Applications:
Guidance and control of the Minuteman I ICBM.

Programming and numerical system:

Number system: Binary, fixed point, 2's complement

Logic levels: 0 or False, OV; 1 or True, -10V

Data word length (bits): 11 or 24 (double precision)

Instruction word length (bits): 24

Binary digits/word: 27

Instructions/word: 1

Instruction type: One and half address

Number of instructions: 39 types from a 4-bit op code by using five bits of the operand address field for instructions which do not access memory.

Execution times:

Add (microseconds): 78 1/8

Multiply (µs): 546 7/8 or 1,015 5/8 (double precision)

Divide: (software)

(Note: Parallel processing such as two simultaneous single precision operations is permitted without additional execution time.)

Clock channel: 345.6 Hz

Addressing:

Direct addressing of entire memory

Two-address (unflagged) and three-address (flagged) instructions

Memory:

Word length (bits): 24 plus 5 timing

Type: Ferrous-oxide-coated NDRO disk

Cycle time (µs): 78 1/8 (minimal)

Capacity (words): 5,454 or 2,727 (double precision)

Input/output:

Input lines: 48 digital

Output lines: 28 digital

12 analog

3 pulse

Program: 800 5-bit char/s

Instruction word format:

    +--------+--------+------+--------+---------+--------+--------+

    |   TP   | T24 21 | 20   | 19  13 | 12    8 | 7    1 |   0    |

    +--------+--------+------+--------+---------+--------+--------+

    | Timing | OP     | Flag | Next   | Channel | Sector | Timing |

    |        |        |      | Inst.  |         |        |        |

    |        |        |      | Sector |         |        |        |

    +--------+--------+------+--------+---------+--------+--------+

Registers:

Phase and voltage output registers

Arithmetic unit (rxcluding storage access):

Add: 78 µs

Multiply: 1,016 µs

Construction (arithmetic unit only): transistor-diode logic is used.

Timing: Synchronous

Operation: Sequential

Storage

Medium	No. of Words	Access (µs)
Rotating disk	2,688	5,000 avg.	(gen. purp. channels)	Rotating disk	41		(rapid access poops)			40	(1 word loop)			160	(4 word loop)			320	(8 word loop)			640	(16 word loop)

Input

48 digital lines (input)

26 specialized incremental inputs

-Medium- -Speed-
Paper/Mylar Tape 600 chars/sec
Keyboard Manual
Typewriter Manual

OUTPUT
-Medium- -Speed-
Printer Character 78.5–2,433 ms (Program Control)
Phase - Voltage (Program Control)

28 digital lines (output)
12 analog lines (output)
13 pulse lines (output)
25,600 word/s maximum I/O transfer rate
Physical characteristics

Dimensions: 20 in high, 29 in diameter, 5 in deep

Power: 28 VDC at 25 A

Circuits: DRL and DTL

Weight: 62 pounds (28.1 kg)

Construction:

Double copper clad, gold plated, glass fiber laminate, flexible polyurethane

Polyurethane

A polyurethane is any polymer composed of a chain of organic units joined by carbamate links. Polyurethane polymers are formed through step-growth polymerization, by reacting a monomer with another monomer in the presence of a catalyst.Polyurethanes are...

-coated circuit boards

Software:

Minimal delay coding using machine language

Modular special-purpose subroutines

Reliability: 5.5 years MTBF

Checking features:
Parity on fill and on character outputs

Power, space, weight, and site preparation

Power, computer: 0.25 kW

Air conditioner: Closed system

Volume, computer: 1.55 cu ft (43.9 l)

Weight, computer: 70 lb (31.8 kg)

Designed specifically to fit in cylindrical guidance package.

The word length for this computer Is 27 bits, of which 24 are used In computation. The remaining 3 bits are spare and synchronizing bits. The memory storage capability consists of a 6000 rpm magnetic disk with a storage capacity of 2985 words of which 2728 are addressable. The contents of memory include 20 cold-storage channels of 128 sectors (words) each, a hot-storage channel of 128 sectors, four rapid access loops (U,F,E,H) of 1, 4, 8, and 16 words respectively, four 1-word arithmetic loops (A, L,H,I), and a two 4-word input buffer input loops (V,R).

The outputs that can be realized from the D-17B computer are binary, discrete, single character, phase register status, telemetry, and voltage outputs. Binary outputs are computer generated levels of +1 or −1 available on the binary output lines.

Instruction set

D-17B Instruction Repertoire



Numeric Code		Code	Description

------------		----	-----------

00 20, s 		SAL 	Split accumulator left shift

00 22, s 		ALS 	Accumulator left shift

00 24, 2 		SLL 	Split left word left shift

00 26, r 		SLR 	Split left word right shift

00 30, s 		SAR 	Split accumulator right shift

00 32, s 		ARS 	Accumulator right shift

00 34, s 		SRL 	Split right word left shift

00 36, s 		SRR 	Split right word right shift

00 60, s 		COA 	Character output A

04  c, S 		SCL 	Split Compare and .ivt

10  c, S 		TMI 	Transfer on minus

20  c, s 		SMP 	Split multiply

24  c, s 		MPY 	Multiply

30  c, s 		SMM 	Split multiply modified

34  c, s 		MPM 	Multiply modified

40 02, s 		BOC 	Binary output C

40 10, s 		BCA 	Binary output A

40 12, s 		BOB 	Binary output B

40 20, s 		RSD 	Reset detector

40 22, s 		HPR 	Halt and Proceed

40 26, s 		DOA 	Discrete output A

40 30, s 		VOA 	Voltage output A

40 32, s 		VOB 	Voltage output B

40 34, s 		VOC 	Voltage output C

40 40, s 		ANA 	And to accumulator

40 44, s 		MIM 	Minus magnitude

40 46, s 		COM 	Complement

40 50, s 		DIB 	Discrete input B

40 52, s 		DIA 	Discrete input A

40 60, s 		HFC 	Halt fine countdown

40 70, s 		LPR 	Load phase register

44  c, s 		CIA 	Clear and Add

50  c, s 		TRA 	Transfer

54  c, s 		STO 	Store accumulator

60  c, s 		SAD 	Split add

64  c, s 		ADD 	Add

70  c, s 		SSU 	Split subtract

74  c, s 		SUB 	Subtract

Special features of the D-17B computer include flag store, split-word arithmetic, and minimized access timing. Flag store provides the capability of storing the present contents of the accumulator while executing the next Instruction. Split-word arithmetic is used in performing arithmetic operations on both halves of a split word at the same time. A split word on the D-17B consists of 11 bits. Minimized access timing is the placing of instructions and data in memory so that they are available with minimum delay from the disk memory.

Guidance software

Autonetics

Autonetics

Autonetics was a division of North American Aviation. Through a series of mergers, Autonetics is now part of Boeing.- General Background of the Anaheim Facility :...

 was the associate contractor for the Minuteman (MM) guidance system, which included the flight and prelaunch software. This software was programmed in assembly language into a D17 disk computer. TRW

TRW

TRW Inc. was an American corporation involved in a variety of businesses, mainly aerospace, automotive, and credit reporting. It was a pioneer in multiple fields including electronic components, integrated circuits, computers, software and systems engineering. TRW built many spacecraft,...

 provided the guidance equations that Autonetics programmed and was also responsible for the verification of the flight software. When MM I became operational, the flight computer was the only digital computer in the system. The targeting was done at Strategic Air Command (SAC) Headquarters by the Operational Targeting Program developed by TRW to execute on an IBM 709 mainframe computer.

Sylvania Electronics Systems was selected to develop the first ground-based command and control system using a programmable computer. They developed the software, the message processing and control unit for Wing 6. To support the deployment of the Wing 6 system, TRW, Inc. developed the execution plan program (EPP) from a mainframe computer at SAC and performed an independent checkout of the command and control software. The EPP assisted in assigning targets and launch time for the missiles.

The MM II missile was deployed with a D-37C

D-37C

The D-37C is the computer component of the all-inertial NS-17 Missile Guidance Set for accurately navigating to its target thousands of miles away. The NS-17 MGS was used in the Minuteman II ICBM...

 disk computer. Autonetics also programmed functional simulators and the code inserter verifier that was used at Wing headquarters to generate and test the flight program codes to go into the airborne computer.