Talk:Orthogonal instruction set

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Whoa man! Nice piece-o' cleanup!!! :-D

Thanks for your kind words! I spent 24 years at DEC, including time in PDP-11, VAX, and VMS Engineering, so this stuff was my bread-and-butter. Atlant 21:04, 2 Jan 2005 (UTC)

Contents

[edit] Badly structured

Specifically, a computer's instruction set is said to be orthogonal if any instruction can use data of any type via any addressing mode. -- the information contained in this sentence should be in the lead paragraph. Shinobu 17:04, 30 March 2006 (UTC)

[edit] Incorrect definition?

I had never heard of orthogonal instruction sets before, but by analogy with orthogonality in mathematics, I suspect the definition should include the fact that all instructions have the same format, with separate fields for the operation and the operands (as described later in the article). The definition given, "Any instruction can use data of any type via any addressing mode", looks analogous to a mathematical basis; in fact, what caught my attention was the last sentence in the definition section, "As with a set of mathematical basis vectors, which must be orthogonal if they are to represent any vector uniquely (...)", which is incorrect, as the vectors of a basis do not need to be orthogonal to represent every vector uniquely. It is theoretically possible to create an instruction set which allowed every possible combination of operations and data locations, but in which using the same operation with different locations, or the same addresses with different operations, would require completely different instruction formats; as I see it, this should not be called an orthogonal instruction set.

I haven't edited the article because I don't know if the definition is really wrong, but the FOLDOC definition looks more appropriate: An instruction set where all (or most) instructions have the same format and all registers and addressing modes can be used interchangeably - the choices of op code, register, and addressing mode are mutually independent (loosely speaking, the choices are "orthogonal").

-- Davitf 18:03, 18 July 2006 (UTC)

[edit] Computer engineering?

Intro sentence: shouldn't this be a term used in computer engineering rather than computer science? --IanOsgood 20:58, 18 July 2006 (UTC)

[edit] "Very strongly"?

"With the exception of its floating point instructions, the PDP-11 was very strongly orthogonal."

Whoa! The definition of orthogonality given sounds like a boolean property. Now you're telling me it's possible to be "very strongly orthogonal", too? (Can you be merely "strongly orthogonal", or even "weakly orthogonal"?) —Preceding unsigned comment added by 69.71.164.107 (talk) 08:17, 24 January 2008 (UTC)

[edit] the assembly language "hid" some of this separation

Isn't "hid" a typo? —Preceding unsigned comment added by 158.194.65.50 (talk) 13:06, 18 February 2008 (UTC)