Amiga - a 16bit or 32bit machine?

[sim085]

Hi,

While on these forums I learnt that Amiga was a 16bit machine. However I read this on wikipedia:

"While the M68k is a 32-bit processor, the version originally used in the Amiga, the 68000, has a 16-bit external data bus so it must transfer 32 bits of data in two consecutive steps, a technique called multiplexing — all this is transparent to the software, which was 32-bit from the beginning. The original machine was generally referred to in the press as a 16-bit computer;"

So does that make Amiga a 16bit machine or a 32bit machine? Considering that the software was written as if for a 32bit machine.

Regards,
Sim085

[wolfchild]

Interesting question...
 
I would call the A1000, A500, A600 and A2000 16-bit machines as they have a 16-bit data bus. Their architecture is 16-bit as well.
 
The AGA Amigas are 32-bit as they have a 32-bit data bus. I think the AGA chipset also makes use of a 32-bit data bus, making these models true 32-bit.
 
I don't know how to classify the A3000. I think it had a 32-bit data bus, but the chipset only used 16-bit.
 
The 68k CPU used to be called a 16/32-bit CPU, so maybe one could call the non-AGA models as 16/32-bit computers, even though it sounds clumsy.
 
Cheers!
Edwin

[spirantho]

And now you know where the Atari ST (Sixteen/Thirty-two) got its name from.

Generally, though: 68000/68010 = 16bit, >=68020 = 32bit.

[chiark]

well, the 68k has a 16 bit data bus, internal 32 bit data registers and a 24 bit addressing...

So it all depends on how you choose your definition of 32 bit .  I agree with Edwin, above.

I believe the 3000 did have a 32 bit data path though.

[sim085]

However was the software for all the Amigas written as if as for a 32bit machine?

[Speelgoedmannetje]

I don't know how to classify the A3000. I think it had a 32-bit data bus, but the chipset only used 16-bit.

And we should never underestimate the chipset. See the Atari Jaguar.

[Caius]

However was the software for all the Amigas written as if as for a 32bit machine?

Unfortunately not. The worst example (in my opinion) is that in the old days some programmers treated it more like a 24bit computer (since the 68000 has 24bit addressing as chiark says), they would then use the upper 8 bits for storing other data to save a little memory. This kind of technique will generally fail on a 32bit system.

[Karlos]

One commonly used definition of width as understood by compilers is the width of a general purpose register. In that regard, the amiga is and always was a 32-bit machine.

[ChaosLord]

All Amigas are 32-bit, end of discussion.

[bloodline]

One commonly used definition of width as understood by compilers is the width of a general purpose register. In that regard, the amiga is and always was a 32-bit machine.

That would be my definition too.

[Piru]

The GP register width is the most used definition. All amigas are 32-bit.

[Speelgoedmannetje]

The whole thing about bits is nonsense anyway. Every computer/console has it's unique chipset with it's pro's and cons, so why talk about the bits?

I like the comparison between the Playstation 2 and the Dreamcast. While the Playstation 2 can show a lot more polygons (16 million, while the Dreamcast can only show 3 million), the Dreamcast has the trick up it's sleeve, for not rendering those polygons which aren't visible. As you see, the whole comparison becomes a lot more complicated.
Add to that how well the system can be programmed, how skilled the programmers are, and voila! There you have the end of the discussion!

[wolfchild]

@Karlos and @Piru

Thanks for the tip.  So 32-bit it is

Edwin

[xeron]

for not rendering those polygons which aren't visible.

I imagine most 3D engines that run on the PS2 do backface culling, at the very least. There are many, many methods to throw away non-visible polygons, and leaving it until the hardware is about to render them is not a good idea. Really, you want to throw away non-visible polygons as early as possible.

[itix]

I would say it is 32bit software running on 16bit hardware. If you are a hardware guy Amiga is clearly 16bit. If you are a software guy Amiga is 32bit.