Amiga - a 16bit or 32bit machine?

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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.

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Usually the CPU (data bus) defines whether the machine is called 16 or 32 bit

Usually the Data bus and the general purpose registers are the same width...

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Not necessarily:
- Z80
- 68008 (!)
- 68000
- 8088
- Pentium (32 bit registers vs. 64 bit bus)
- ...

Well... obviously apart from all the CPU's that don't... :lol:

Win   +1

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A 16-bit address bus would be more of a problem. It would limit you to 64K address space. I'm not sure if the 680x0 is capable of running on a "narrow" address bus in the same way it does a data bus.

Yup, the Falcon suffered with a 16bit Data bus. The address bus can't be "multicycled" like the data bus.

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Well, that's not exactly how I remember it. It clearly wasn't designed as a full-fledged 32-bit cpu since important internal structures are only 16-bit.

It was realized that 16-bits did not provide enough address space, and rather than choosing some page-mode or other kludge they went all 32-bit on the address space. Only the lower 24 bits were routed to external pins as a means to keep pin count down and 16 MiB ought to be enough for everybody!

In order to avoid the mess with different sized address and data registers, the data registers too became 32-bit wide. The external data bus was only 16-bits though, probably to keep pin count down, but also maybe because 16-bit ops were thought of as the primary mode of operation and the slower 32-bit ops were only icing on the cake sort of speak...

The 68000 was designed to be comparable to the minicomputers of the time, like the PDP and the VAX... thus it's similarity to their architecture, including a 32bit data/address  model.

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IMHO the P4 was pretty much a monstrosity right from the start, built entirely for high clock rates on paper - performance came second.

Yeah, I second that!

The Pentium4 was the most atrocious architecture ever... I was an Athlon guy at that time.

The P4 was nothing more than an exercise in marketing... "Hey let's pump this CPU to 3Hgz!!!"... no regard for actual real world performance... That CPU killed the Pentium brand, the intel "Core" architecture was a breath of fresh air... and rather AMD like