[jmagar]

Carmack or Michael Abrash? Read Graphics Programming Black Book ( http://www.amazon.com/Michael-Abrashs-Graphics-Programming-S... )

Abrash did amazing things with assembly to get Quake to run on the 486.

I don't know if Carmack, Abrash, or someone at SGI (it's in OpenGL source code too) came up with it; but it seems like witch craft to me.

[thisisnotmyname]

Or none of the above? http://www.beyond3d.com/content/articles/8/

[gcv]

According to this article, neither of them: http://www.beyond3d.com/content/articles/8/

That article also links to a paper (http://www.lomont.org/Math/Papers/2003/InvSqrt.pdf) analyzing the initial approximation constant.

[andrewf]

The Black Book is available as PDFs from http://www.gamedev.net/reference/articles/article1698.asp

Byte.com hosted a copy for a long time, but that seems to have issues atm.

[weavejester]

I had a 486 when Quake came out. The framerate was far too low to make it playable. I remember trying to play the demo, and I had to cut the screen down to the size of a postcard (something like 160x100) to get a framerate of 25fps.

The first Pentiums, on the other hand, were more than up to the job.

[dangrover]

The 486!? Wow

[MikeCapone]

Yeah, I actually played it (choppily) for a while on my 486.