What makes the 68k processors so cool?

[Bunsen]

Over at SegaRetro is the best reasonably noob-friendly explanation I've discovered yet of the powerful features of the 68k family, why programmers and system builders were drawn to it, and the shortcomings of the 68000 which were addressed in later models in the series.

http://segaretro.org/Motorola_68000

 

[TheWhiteFalcon]

Heatsinks?

...I'll show myself out.

 

[Powertrip]

Very cool find! I was also not aware of that community.

 

[Elfen]

Interesting! Time to start digging deep.

 

[Bunsen]

And from a fansite about TI calculators, the m68k FAQ. 

Seems to cover just about every 68k-related CPU ever made, including many of their common peripherals, and later 68k-derived / 68k-core microcontrollers with integrated peripherals for specific embedded uses, development tools, compilers, simulators, emulators, debuggers, industrial computers, embedded and development boards, as well as early PPCs.

And it's a plain text file, so *yoink*.

 

[Bunsen]

ever made

Last-modified: 1996/01/06

Version: 22

comp.sys.m68k

 

[Sherry Haibara]

They still teach us the 68k assembly and microcode at my university - from an architectural point of view, it's an incredibly elegant design.

Much more convenient to use than the cumbersome syntax of the x86 family, and it provides a great deal of extra flexibility too. 

My favorite feature is probably the (almost) complete orthogonality of the instruction set with respect to the available addressing modes, which is simply *so* cool and convenient, while the x86 uses all kinds of tricks and strange assumptions about which registers you can use with which instructions and so on. 
 

 

[johnklos]

Sherry: What do they teach you about the microcode of the m68k? I think that details about the microcode might be helpful in handling undocumented instructions in emulators and FPGA m68k cores.

What's interesting is that in the pursuit of performance, the m68060 had no microcode - it was a completely hardwired.

 

[rezwits]

There's two things that make the 68k awesome to me.  One is mac related and the other is "era" related.  In the early days, the 68k chips we had, were what Apple wants their chips to be today, and that is QUIET, FAN-LESS, an NO HEATSINK, I don't know about power consumption, but were so much more quieter than late PPC era, Fan Based, with Heat Sinks.  It was like a curve in the idea that "we want speed" at whatever cost, and they did, they put the LOUDEST fans possible.  Honesty, I cannot use my G4 Dual 1.25, can't do it!  It's too loud, it's officially going to be my first doorstop.  I just rescued a G3/266 which is one of the last before the dark (loud) ages, systems that's going to replace it in the "always on team"  I used to have one but I upgraded it to G4, and moved to a humid climate, and it died for some reason, but I moved back to my dry climate.  So it should work like it did when I was here before.  Now that Apple has really good speed, they are saying, OK, let's go back to slowing the chip down, and use less power, heat, noise. etc.

But aside from that, the other thing that I love about 68k, is on the Mac side, you can have TWO FILES! on a disk.  A System File and a Finder, or if you wanna be slick, any App of your choice!  I love that. Think about that for a second?  Windows even 3.1 takes like 500-1000 files to run?  On the mac all you need is simplistically two files!  That's so sick!  I mean I can make my own OS if I want to.  Just make a Finder replacement, or some other app, and you're good to go.

So to me being able to have my 68ks running with a somewhat fan-less way quieter mode, is so key, and then as a tinker device being able to go into the System Folder and seeing just under 400 files to run the OS (7.6.1), that I can manage with my mind and have all memorized, is really great for a (really knowing what's going on) system.

Laters...

But I'm with WhiteFalcon, I'll show myself out, because the only Assembly Programming I was fortunate to get was 8086, UNLV was pretty anti-mac back in the 1990's, unless it was to run Mathematica in the Math Labs on Macs,but in the Computer Science Labs it was Cray, VAX, Sun, or Intel, but we had 30 NeXT Cubes!

 

[uniserver]

personally i think its crazy just how useable an 8mhz with 4megs of ram is.

there is soooo much software, and its not crap... its good software!

 

[Bunsen]

Here's someone building a 68000 computer from the ground up - including designing the entire system architecture, ie, not cloning an existing machine, and writing a monitor ROM for it.  Looks worth following if you're into that kind of thing.

https://hackaday.io/project/7242-motorola-68000-computer

 

[Bunsen]

Heatsinks?

I lolled.

 

[zerobotman]

Here's someone building a 68000 computer from the ground up - including designing the entire system architecture, ie, not cloning an existing machine, and writing a monitor ROM for it.  Looks worth following if you're into that kind of thing.

https://hackaday.io/project/7242-motorola-68000-computer

We all know real men build their homebrew computers with 74 series logic gates on protoboard

http://cpuville.com/

 

[Elfen]

DAMN... I built my first CPU back in 1976 (or so) from an article on Popular Electronics. But due to a misprint on their diagram - it did not pass the "Smoke Test" and this 13yo was not happy in his project going up in flames!

Sure, they posted up an errata and an apology on the following issue but for me it was too late. GRRRR....!

(This was not it but this was the one after it, I believe: http://incolor.inebraska.com/bill_r/elf/html/elf-1-33.htm )

 

[commodorejohn]

Heh, I'd like to try my hand at a homebrew CPU sometime, but I'd need to brush up on my low-level electronics knowledge a good deal first...

 

[uniserver]

For me its the the assembly written software....   its just really great....   so efficient.

 

[Bunsen]

Well in fairness, hand-tuned assembly will bring out the best of any CPU.  I'm just fascinated by the kind of architectural features that drew programmers to the family when it first came out.  The first 68k was spoken of as a "mainframe on a chip" at the time, I understand its architecture was heavily inspired by the PDP-11.

 

[commodorejohn]

The first 68k was spoken of as a "mainframe on a chip" at the time, I understand its architecture was heavily inspired by the PDP-11.

Quite a bit, yes. Aside from a couple oddities like the division between address and data registers, it basically looks like a 32-bit PDP-11 as designed by someone who hadn't seen the VAX.

 

[NJRoadfan]

They taught VAX assembly at my university. It was.... interesting. That CPU had an opcode for everything! People will say the 6502 is elegant too... as long as nothing needed to go over 255! The 65c816 fixed that, but kept the annoying 64k segmented memory model.

x86 ASM is ugly, but somehow prevailed despite how many attempts were made to replace it. Now its got more opcodes than a VAX!