D - 17B 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 , 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 extensively and only using DTL ( diode - transistor ) logic 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 rotating disk memory , with non - destructive readout ( NDRO ) , also enhanced the reliability of the computer . In actual , real - time situations involving Minuteman missiles , the mean time between failures ( MTBF ) was over 5 . 5 years . 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 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 : Clock channel : 345 . 6 Hz Addressing : Memory : Input / output : Instruction word format : Registers : Arithmetic unit ( excluding storage access ) : Construction ( arithmetic unit only ) : transistor - diode logic is used . Input OUTPUT 28 digital lines ( output ) 12 analog lines ( output ) 13 pulse lines ( output ) 25 , 600 word / s maximum I / O transfer rate Physical characteristics Construction : Software : Reliability : 5 . 5 years MTBF Checking features : Parity on fill and on character outputs Power , space , weight , and site preparation 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 . 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 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 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 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 .