[A89] Re: 68K Guide


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[A89] Re: 68K Guide



Actially, the difference between pi and pentium pro are smaller than the 
differences between pentium pro and pii.

The original pentium was basically a 386 and a 486 thrown togeather on one 
piece of silicon. The p pro introduced advanced branch prediction, lots of 
virtual register, channel-less  instruction handeling, and several other 
features that really only matter if you are into fine-optomizing assembly.

>From a programming perspective, the biggest difference between pi and p pro 
(or pii if you preffer) is mmx, which allows you to use large floating point 
registers as several int registers of whatever size you want. It was niffty.

Overall, the evolution of 80x86 has had less to do with hardware than 
software. Most new instructions are suefull but not necessary.  Memory, on 
the other hand, is crucial, and without win95 or a dos extender, it was a 
royal pain to use more than 1mb total.

The 286 introduced "protected memory" which was intended to allow you to use 
large blocks of memory safely, but in actuality, it was extreemely error 
prone and tedious.
With the 386 the mechanism became somewhat usable, but only at an os level. 
Most people were still stuck with either 1mb ram, or using LIM's 'expanded 
memory' or ems. But again, it was slow and error prone without additional 
software.

A little later, Extended memory became available. There was a lot more of 
it, and it caused slightly fewer crashes, but was still rediculously 
difficult to use. Most programmers used third party memory-management 
freeware that often doubled the size of their programs.

But, since win95 (3.x was a nightmare), "flat real mode" became very common. 
Flat memory is where you have a 4gb address space that the calling program 
(i.e. win95) sets up for you, and you get to forget that your ram is 
scattered all across the system memory and probably also the user's hard 
drive.
Since then, all programs for pcs have been written in flat mode.

Anyway, dealing with the different mechanisms was the trickiest part of 
80x86 asm. I have learned 5 or 6 assembly languages (pluss dozzens of high 
level programming, scripting, and markup languages) and its instructions are 
not rediculously difficult. Its making large programs for pre-win95 systems 
that is hard.


Back to the original question: Should you learn 80x86 and 68k at the same 
time. It will be only slightly easier to learn 68k after 80x86. If you are 
interrested in learning several assembler languages, though, then those two 
are a good start. They are about as different as macroprocessers get, and 
the experience could come in handy in the future. Neither will help you much 
with risc programming, etc, though. Whether you should do both depends on 
what you want out of it.

I apologize for the length.


>From: "Lord Drantin" <DRANTIN@cablelynx.com>
>Reply-To: assembly-89@lists.ticalc.org
>To: <assembly-89@lists.ticalc.org>
>Subject: [A89] Re: 68K Guide
>Date: Thu, 12 Jun 2003 19:01:48 -0500
>
>What's new?
>MMX
>SSE1
>SSE2
>3DNow!
>
>anything you've heard of like those are additions to the instruction set...
>

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