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How Computers Calculate - the ALU: Crash Course Computer Science #5
11:10

How Computers Calculate - the ALU: Crash Course Computer Science #5

Today we're going to talk about a fundamental part of all modern computers. The thing that basically everything else uses - the Arithmetic and Logic Unit (or the ALU). The ALU may not have to most exciting name, but it is the mathematical brain of a computer and is responsible for all the calculations your computer does! And it's actually not that complicated. So today we're going to use the binary and logic gates we learned in previous episodes to build one from scratch, and then we'll use our newly minted ALU when we construct the heart of a computer, the CPU, in episode 7. *CORRECTION* We got our wires crossed with the Intel 4004, which we discuss later. The 74181 was introduced by Texas Instruments in 1970 but appeared in technical manuals around 1969. The design of the 74181, like most of the 74xx/74xxx series, was an open design which was manufactured by many other companies - Fairchild was one such manufacturer. They produced a chip, the Fairchild 9341, which was pin-for-pin compatible with the 74181. Fairchild was the first to prototype an ALU, building the Fairchild 4711 in 1968 - a one-off device not optimized for scale manufacturing. In 1969, Signetics came out with the 8260, which they marketed in a very limited sense (it was attached, AFAICT, to one particular computer, the Data General SUPERNOVA). TI follows afterwards (March 1970) with the 74181, coupled with the 9341 from Fairchild. The 74181 became the standard number for this part, and was available from many manufacturers (back in those days, chip makers cross-licensed designs all over the place in order to provide assurance that their part could be sourced from multiple manufacturers). Produced in collaboration with PBS Digital Studios: http://youtube.com/pbsdigitalstudios The Latest from PBS Digital Studios: https://www.youtube.com/playlist?list... We’ve got merch! https://store.dftba.com/collections/crashcourse Want to know more about Carrie Anne? https://about.me/carrieannephilbin Want to find Crash Course elsewhere on the internet? Facebook - http://www.facebook.com/YouTubeCrashC... Twitter - http://www.twitter.com/TheCrashCourse Tumblr - http://thecrashcourse.tumblr.com Support Crash Course on Patreon: http://patreon.com/crashcourse CC Kids: http://www.youtube.com/crashcoursekids Want to find Crash Course elsewhere on the internet? Facebook - http://www.facebook.com/YouTubeCrashCourse Twitter - http://www.twitter.com/TheCrashCourse Tumblr - http://thecrashcourse.tumblr.com Support Crash Course on Patreon: http://patreon.com/crashcourse CC Kids: http://www.youtube.com/crashcoursekids
Registers and RAM: Crash Course Computer Science #6
12:17

Registers and RAM: Crash Course Computer Science #6

Take the 2017 PBS Digital Studios Survey: http://surveymonkey.com/r/pbsds2017. Today we’re going to create memory! Using the basic logic gates we discussed in episode 3 we can build a circuit that stores a single bit of information, and then through some clever scaling (and of course many new levels of abstraction) we’ll show you how we can construct the modern random-access memory, or RAM, found in our computers today. RAM is the working memory of a computer. It holds the information that is being executed by the computer and as such is a crucial component for a computer to operate. Next week we’ll use this RAM, and the ALU we made last episode, to help us construct our CPU - the heart of a computer. *CORRECTION* In our 16x16 Latch Matrix graphic, we inadvertently left off the horizontal row access line above the top row of latches. As a result, the highlighted line for the row at address 12 should actually be one line higher. Produced in collaboration with PBS Digital Studios: http://youtube.com/pbsdigitalstudios The Latest from PBS Digital Studios: https://www.youtube.com/playlist?list=PL1mtdjDVOoOqJzeaJAV15Tq0tZ1vKj7ZV We’ve got merch! https://store.dftba.com/collections/crashcourse Want to know more about Carrie Anne? https://about.me/carrieannephilbin Want to find Crash Course elsewhere on the internet? Facebook - http://www.facebook.com/YouTubeCrashC... Twitter - http://www.twitter.com/TheCrashCourse Tumblr - http://thecrashcourse.tumblr.com Support Crash Course on Patreon: http://patreon.com/crashcourse CC Kids: http://www.youtube.com/crashcoursekids Want to find Crash Course elsewhere on the internet? Facebook - http://www.facebook.com/YouTubeCrashC... Twitter - http://www.twitter.com/TheCrashCourse Tumblr - http://thecrashcourse.tumblr.com Support Crash Course on Patreon: http://patreon.com/crashcourse CC Kids: http://www.youtube.com/crashcoursekids
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