I have experience with Scheme, Racket, and Common Lisp, including teaching undergraduate-level courses on programming language paradigms and principles. I am also an avid reader of programming language literature, and for years I've been impressed with what I've read about the Lisp machines of the 1980s, as well as projects inspired by them such as Apple's work on Newton (which started as a Lisp project until John Sculley made an executive decision to have C++ be the implementation language), SK8, and Dylan in the 1990s. However, having being born in the late 1980s, I never got to use a Lisp machine, and the only one I've seen is the LMI-LAMBDA machine in the Computer History Museum in Mountain View, CA.
There's a lot of nostalgia, mystique, and praise surrounding the Symbolics Genera operating system, especially its development environment, which I've heard former users say it was the best development environment they've ever used. However, I haven't heard as much said about Xerox Interlisp-D, which is also a graphical Lisp environment that seems to be influenced from Xerox PARC's earlier work on Smalltalk, Mesa, and Cedar. I'm curious about the similarities and differences between Symbolics Genera and Xerox Interlisp-D. Why is Genera more hyped than Interlisp-D? Unlike Genera, which is proprietary and is extremely difficult to obtain legally, Interlisp-D is now free, open-source software, and there's a community that has ported Interlisp-D to run on top of modern operating systems.
From that perspective the two systems had very different objectives and target audiences.
Interlisp-D was focused on ease of use, the GUI, incremental development by researchers who weren't focused on programming per se. This explains the features around the GUI, error correction, programmer's assistant, source file management. Interlisp was forgiving.
I always imagined Symbolics Genera was designed for the expert user who wanted the most power, speed, capability possible.
Race car to off-track vehicle.
As for hardware, the Xerox D-machines weren't particuarly designed for Lisp. Comparing the hardware is kind of irrelevant.
Today, medley runs 1000 times faster and a much larger address space, so there's enough room to try things.
The Medley Interlisp project includes many "help wanted" items in terms of documentation, testing, Common Lisp compatibility, and things relating to adapting to modern hardware (keyboard, mouse, display) and software (OS, installer, unicode, etc) as well as finishing some "work in progress"items that were done after Medley 2.0. We started with Medley 3.5 to get the larger address space (4 bits) and symbol space.