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December 6th, 2007, 02:48 PM   #1
 
Joined: Dec 2007
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Arithmetic/Logic Unit

In an average computer, where is the arithmetic/logic unit located at? Isn't it part of CPU? Also, doesn't the programming software uses this arithmetic/logic unit to calculate most of the mathematical calculations?
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December 6th, 2007, 06:19 PM   #2
 
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Re: Arithmetic/Logic Unit

Quote:
Originally Posted by johnny
In an average computer, where is the arithmetic/logic unit located at? Isn't it part of CPU? Also, doesn't the programming software uses this arithmetic/logic unit to calculate most of the mathematical calculations?
ALUs are integral to just about everything in computing, so there will typically be many, many, many simple ALUs in any chip in your system. The CPU and GPU, which require a lot of mathematical calculation will have very large and complicated ones. A CPU is theoretically supposed to be able to compute anything, all the other bits are there to help it out, and to pass it inputs, etc...

You may want to check the wikipedia article... Wikipedia is a nerd's best friend.
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December 7th, 2007, 05:02 AM   #3
 
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Re: Arithmetic/Logic Unit

They used to be completely separate from the CPU proper (the 80286 and 80287 were that way, I think) but on the same die. But as you can imagine, the speed of light coupled with modern clock speeds essentially requires that the CPU be touching.
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December 15th, 2007, 09:19 PM   #4
 
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Re: Arithmetic/Logic Unit

Hmmm, if I remember my history correctly (which I probably don't,) the Pentium was the first cpu to incorporate an on-die ALU... or maybe it was the first to incorporate two ALU's. It was probably the latter.
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December 19th, 2007, 10:26 AM   #5
 
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Re: Arithmetic/Logic Unit

Who knows, I don't remember all that well either. Maybe the Pentium was the first that shipped standard with that feature -- the 80287 was optional, I believe.
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February 4th, 2009, 04:48 AM   #6
 
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Yes it is a part of CPU. Yes, programming software uses this arithmetic/logic unit to calculate most of the mathematical calculations.
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April 30th, 2010, 02:08 PM   #7
 
Joined: Apr 2010
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Re: Arithmetic/Logic Unit

Microcontrollers contain an ALU and a CPU
the CPU deals with shifting of data while the ALU does all the math, logic and comparissons...the cpu merely moves the data into the registers allowing the ALU access....if you wish to learn more perhaps you should read my thread on the fetch-execute cycle and if you would like a thread dedicated to how the CPU is set out, the architecture of it internally then pm me and when I have time I would be much obliged.
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August 17th, 2010, 07:16 PM   #8
 
Joined: Aug 2010
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Re: Arithmetic/Logic Unit

Hmm, old topic, but I'll toss in my 2 cents worth anyway.

I think there is some confusion between ALU (arithmetic logic unit) and FPP (floating point processor). The 80287 was an FPP, not an ALU. Back when dinosaurs roamed the earth, and I took my first computer class, The ALU was considered to be part of the CPU, not separate from it. It was the part that did low level things like integer add, subtract, shift, rotate, AND, OR, Complement, etc. The other primary part of the CPU was the program control which handled the program counter, fetching instructions and reading/writing data to/from memory. Of course, over the years, definitions tend to shift a bit.
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