They were also a pretty good computer graphics and computer algebra software company, and both those divisions got sold off and continued their work for a number of years after Symbolics itself went out of business.
It's interesting to note that by the time of Symbolics' demise (I'm placing it at 1993ish, although that's probably not accurate), even IBM realized that developing systems as integrated software/hardware architectures was not feasible.
It's feasible.
Symbolics' systems and the first AS/400 models (the last new hardware/software architecture developed by IBM) are in a totally different class.
If you're curious about the Newton processor: http://www.ot1.com/arm/armchap1.html (see the "ARM6" section).
Thanks for the link.
It did not help.
The basic limitations of Genera: complex interwoven software with lots of legacy stuff, single user, single image, no security ... just did not scale and was not on a growth path.