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

Paul Koning paulkoning at
Thu Sep 15 19:09:26 CDT 2016

> On Sep 15, 2016, at 5:57 PM, Toby Thain <toby at> wrote:
> 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.

So would you call a PDP-8/S a one bit machine?  I suppose you could, but that seems rather odd.


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