Talk:Arithmetic logic unit/Archive 1

Archive 1

History

Few issues... First, von Neumann didn't design ENIAC, though he certainly knew of it and was influenced by its design. Mauchly, Eckert, Brainerd, and Pender are the big names usually associated with ENIAC's design and manufacture. Second, it's pretty debatable whether the ALU was originally suggested for EDVAC or not. It would be good to try to find the first usage of the term and if that cannot be found, you can probably at least mention earlier devices that were more or less ALUs with I/O devices (like the IBM series of tube multipliers, adders, etc with punch card I/O). -- uberpenguin 15:48, 3 January 2006 (UTC)

Difference between ALU and core

There is an emergence of multicore processors. So what's the difference between ALU and core?

An ALU is an execution unit, directed to its chores by the control unit; both those units are part of the CPU core. Today, a core may often contain several ALUs as well as other types of execution units. --Wernher 03:18, 30 October 2005 (UTC)

the ALU is a basic building block of a CPU or CORE.
its the same relationship as the AND gate to the Half Adder as ALU is is to CPU/CORE
the ALU is a very complex and important block that needs more info on it on this page. it is a small part of a cpu core but its prob the most complex part and critical part to understanding how a cpu works. Eadthem (talk) 03:55, 28 December 2007 (UTC)

Division/Multiplication

Is it not true that division/multiplication can be done by bitwise shifting and addition/subtraction?—Preceding unsigned comment added by 60.240.107.52 (talk • contribs)

• I think this is the answer to your question --ZeWrestler ^Talk 17:34, 11 November 2006 (UTC)

hmm, can you give me a history about the arithmetic Logic Unit —Preceding unsigned comment added by Wert zieta (talk • contribs) 02:56, 20 August 2008 (UTC)

schematic typo

I think F in the schematic should be called operator not operand? A and B are the operands. See http://en.wikipedia.org/wiki/Operand SvenPB (talk) 09:56, 8 February 2009 (UTC)

Is the 74AS888 an ALU?

PeterCamilleri (talk) 18:09, 28 July 2009 (UTC)OK; I have dug up more details and this is an impressive part. Too bad it came out too late to have a real impact. That however is opinion. What is not opinion is that this is NOT just an ALU. The TI data sheet calls it an 8 Bit Processor Slice. If you compare features, this part is actually a superset of the AM2901/2903 bit slices.

--PeterCamilleri (talk) 17:22, 11 May 2009 (UTC)

Computing without an ALU

I know of two computers that did not include ALU's; instead, they used a table lookup to do adds. Theses were the IBM 1620 (Can't Add; Doesn't Even Try) and RCA 301. I don't know whether anyone ever did it for production programs, but you could do octal arithentic by changing the add tables. Shmuel (Seymour J.) Metz Username:Chatul (talk) 15:02, 22 September 2010 (UTC)

Decimal representations

I know of several decimal computers, and none of them used ten tubes per digit. If there is such a beast, then a citation should be provided and the clause even true decimal systems, with ten tubes per digit split into two clauses, e.g., decimal computers using binary representations of the digits and even true decimal systems, with ten tubes per digit. Shmuel (Seymour J.) Metz Username:Chatul (talk) 15:34, 23 November 2010 (UTC)

Practical overview

This entire section needs to be re-written. Who is 'the customer' and it is ambiguous what the costs refer to, are we talking energy, monetary costs, complexity costs? Also is it really relevant in understanding what an ALU is to emphasize that better ALUs will cost more? Isn't that obvious enough to be omitted? — Preceding unsigned comment added by 58.107.82.54 (talk) 03:55, 26 September 2013 (UTC)

Reciprocal approximate?

The ALU on the Cray-1 did not have divide circuitry, but instead implemented Reciprocal approximation and Reciprocal iteration, as explained in Cray-1 Computer System Hardware Reference Manual (PDF). Cray Research. p. 3–28. 2240004. {{cite book}}: Cite has empty unknown parameters: |author-name-separator=, |doi_brokendate=, |deadurl=, |laydate=, |subscription=, |nopp=, |trans_title=, |trans_chapter=, |laysource=, |laysummary=, |author-separator=, |lastauthoramp=, |registration=, and |chapterurl= (help); Unknown parameter |separator= ignored (help)CS1 maint: extra punctuation (link) CS1 maint: postscript (link) Does this belong in the article, or is it TMI? Shmuel (Seymour J.) Metz Username:Chatul (talk) 17:33, 3 December 2013 (UTC)

ALU not for division?

The statement that ALUs don't usually do division is silly. Historically, the vast majority of ALUs produced commercially as primary processing units have had support for integer division and a modulus operation. Check out the PDP-8 instruction set, as an example, or ANY of the references, external links, "see also"s....

Anyway, it seems like that section was cribbed directly from another source that didn't know what it was talking about. — Preceding unsigned comment added by 75.156.103.185 (talk) 16:33, 4 December 2013 (UTC)

ALU Diagram

The ALU diagram contains some letters, such as "F" which are never documented in the text. This is very confusing. — Preceding unsigned comment added by WirlWhind (talk • contribs) 19:06, 7 January 2014 (UTC)

Complex operations

The whole Complex operations section is problematic. Phrases like "Design an extraordinarily complex ALU" and "Tell the programmers" make it read like it's part of a manual or something. So I've tagged it with {Inappropriate tone} and added a few "HTML comments" here and there. - dcljr (talk) 19:33, 11 January 2011 (UTC)

I disagree. The section explains the issues in a manner that I find clear; or are you concerned with the use of the word "complex" & "simple" here? BTW, I am not a chip designer by any measure; I don't even know how to code or read assembler. -- llywrch (talk) 19:49, 24 March 2011 (iTC)

The issue is that it appears the article is giving instructions to the reader, as though it were telling you to do something. --Mman2112 (talk) 18:24, 7 March 2014 (UTC)