Meaning of "architecture width" - Re: 68K Macs with MacOS 7.5 still in production use...

Camiel Vanderhoeven iamcamiel at
Fri Sep 16 01:32:46 CDT 2016

Op 15 sep. 2016 11:57 p.m. schreef "Toby Thain" <toby at>:
> On 2016-09-15 2:38 PM, Noel Chiappa wrote:
>>     > From: Chuck Guzis
>>     > Call it anything you want, but we know what Motorola called it.
>> The _first implementation_ may have been 16-bit, but I am in no doubt
>> whatsover (having written a lot of assembler code for the 68K family)
>> that the _architecture_ was 32-bit:
>> - 32-bit registers
>> - many operations (arithmetical, logical, etc) defined for that length
>> - 32-bit addresses
> GPR width, being the visible programmer model, is the most common and
convenient definition of "architecture" I've come across. But there's no
reason we can't just say the *visible* architecture is 32 bit (which it
is), but the "internal" architecture is sort of 16.

Afaik, the term computer architecture was coined for the IBM 360, which was
a 32-bit architecture, with 8, 16, 32, and 64 bit implementations. The term
architecture specifically refers to what the programmer sees, not to the
specifics of an implementation.


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