The assembler will recieve a GC-OVERFLOW interrupt. Other TT2500
files set the GC-OVERFLOW variable to a dummy function, which seems to
appease the interrupt.
Since the TVDIS code was written before backquote was introduced to
Maclisp, it uses comma characters without quoting. To accomodate this
a call to SETSYNTAX overrides the new syntax for comma.
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