You must be using a very narrow definition of "hardware architecture". In the 68K era Apple used to custom-design pretty much everything interesting in the box except the processor and memory. The IIfx was perhaps the most extreme example (several custom ASICs and two 6502-based I/O coprocessors, IIRC). For the Newton we even designed parts of the processor (e.g., the MMU).

Let's take your example of the IIfx: off the shelf 68k processor on NuBus. ASICs and I/O coprocessors are just devices. Granted I didn't know about the custom processor work on the Newton, but if IIfx counts as a new hardware architecture, then so does the x86 move from ISA and 8259A to PCI-E and APIC. And I don't think it makes sense to argue that today's Macs have anything resembling a custom architecture.

Symbolics' systems and the first AS/400 models (the last new hardware/software architecture developed by IBM) are in a totally different class.

Fair enough: sounds like your definition of "hardware architecture" is limited to the processor itself.

If you're curious about the Newton processor: http://www.ot1.com/arm/armchap1.html (see the "ARM6" section).

Well, processor and memory (I certainly think NUMA machines are different), everything else is pretty much just I/O.

Thanks for the link.