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Guy Harris (talk | contribs) →Microcode: The claim made in that sentence is supported by the same page in the Encyclopedia of Library and Information Science that the previous sentence's claim is. |
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[[Emulator|emulated]] by the [[microprogram]].<ref name="30theory">{{cite book|url=http://bitsavers.org/pdf/ibm/360/fe/2030/Y24-3360-1_2030_FE_Theory_Opns_Jun67.pdf|title=Field Engineering Theory of Operation, 2030 Processing Unit, System/360 Model 30|id=Y24-3360-1|edition=Fifth|date=June 1967|publisher=IBM}}</ref><ref>{{cite book|url=http://bitsavers.org/pdf/ibm/360/fe/2030/Model_30_Microprogramming_Lang.pdf|title=Model 30 Microprogramming Language|publisher=IBM}}</ref> Handling a 4-byte word took (at least) 6 microseconds, based on a 1.5 microsecond storage access cycle time.<ref name="30theory"/>{{rp|pg.1–4}}
The microcode was stored in [[CCROS]] (Card Capacitor Read-Only Storage) developed in Endicott. The Model 30 and Model 40 were originally supposed to share the [[Transformer Read Only Storage]] (TROS) being developed at [[IBM Hursley]], but CCROS was cheaper to manufacture.<ref name= ibmbook/> This system used [[Mylar]] cards the size and shape of a standard IBM [[punched-card]], so the microcode could be changed using a [[keypunch]]. Each card held 720 bits, and the total microcode consisted of 4032 60-bit words. The Mylar "encased copper tabs and access lines."<ref name="encyc">{{cite book |last1=Kent (ed.) |first1=Allen |title=Encyclopedia of Library and Information Science: Volume 69 - Supplement 32 |date=2000 |publisher=CRC Press |isbn=0-8247-2069-5 |page=267 |url=https://books.google.com/books?id=1U_gOuKGFYYC&pg=PA267 |accessdate=Dec 3, 2018}}</ref> A hole punched at a specific ___location removed the copper tab and encoded a zero, unpunched locations were read as ones.
==System configuration==
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