What does "No more room for LISP objects" mean?

[Calvin Clark <ckclark@MIT.EDU>]

This is probably a stupid question, but bear with me; I'm new to Common
Lisp.  Sometimes, when compiling large packages like garnet, I get the
error:

	No more room for LISP objects

and I'm not sure what this means.  What boundary am I hitting?  This
occurs even when the clisp process is not taking up a lot of memory
compared to the real memory of the system.  If this error indicates that
the process is hitting a system resource limit, which one is it?  If
not, is there some way I can modify the source so that this won't happen?

(BTW, I've only seen this error on DECstation/ULTRIX, not on Sparc/Solaris.)

A (possibly) related question: can someone explain the output of the clisp
``room'' function, which seems to be still CLtL1, since it takes no
arguments?

-Calvin