Microprogramming: History and Evolution - Edwardbosworth.com
Microprogramming: History and Evolution - Edwardbosworth.com
Microprogramming: History and Evolution - Edwardbosworth.com
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Problems in the 1950’s<br />
In 1958, the EDSAC 2 became operational; it was the first microprogrammed <strong>com</strong>puter.<br />
The control unit used ROM made from magnetic cores (Hennessy & Patterson, 1990).<br />
There were two reasons that Wilkes’ idea did not take off in the 1950’s.<br />
1. The simple instruction sets of the time did not dem<strong>and</strong> microprogramming, <strong>and</strong><br />
2. The methods for fabricating a microprogram control store were not adequate.<br />
All of this changed when IBM embraced microprogramming as a method for the<br />
control units of their System/360 design.<br />
We should note that the early control stores for the IBM System/360 were implemented<br />
with technologies that are no obsolete <strong>and</strong> strange to our ears.<br />
BCROS<br />
TROS<br />
CCROS<br />
Balanced Capacitor Read–Only Storage<br />
Two capacitors per word in a storage of 2816 words of 100 bits each.<br />
Transformer Read–Only Storage.<br />
Magnetic core storage of 8192 words of 54 bits each.<br />
Card Capacitor Read–Only Storage.<br />
Mylar cards the size of st<strong>and</strong>ard punch cards with copper tabs.
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