Most University labs had a machine room where the Symbolics machines (if they had those) were standing (large, too noisy fans, drawing 1 kw or more electricity, ...). Cables for the console (1 Megapixel b/w screen, keyboard, mouse and digital audio) went from there into the offices. All one could hear were the clicks from the Symbolics mechanical keyboards.
The LMI and Explorer machines had some interesting hardware stuff. Too bad, that both companies left the business very early ...
Accelerators were available for the Symbolics machines, too. IIRC there were DSPs. Also an interface to the Pixar Image Computer and to Connection Machines. Or the FrameThrower, a programmable Framebuffer.