The_neglected_art_of_Fixed_Point_arithmetic_20060913.pdf

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The neglected art of

Fixed Point arithmetic

Seminar Presentation

Assembly 2006, 3

- 6

August 2006

(Revised: September 13, 2006)

Jetro Lauha

Contents

●

Motivation

Introduction

Typically needed functions

Caveats and tricks

Tips for making a fixed point library

Motivation

●

Man sent himself to moon, and space probes

even beyond that.

Do you think the hardware

used to accomplish those feats had fancy FPU

to do all the calculations?

They used RCA 1802.

–

●

Processing power equals roughly 6502 or 6510,

used in Apple II and Commodore 64.

Motivation

●

But it's a lot of work.

–

30% of the Apollo software development effort was

spent on scaling.

[KrL64]

●

So they eventually switched to floating point when

hardware got better.

Motivation

●

So why am I talking about this?

–

Well, at least it's COOL, in retro-way:

This is how demo & game coders did their 3D stuff

15 years ago and made some pretty cool stuff even

with the minuscule CPU power.

●

But does that matter anymore – except if you

are going to take part in the old school demo

competition with some retro stuff?

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