64-bit LispWorks for Linux now automatically adjusts its default heap size on startup, depending the age of the operating system.
On old Linux systems the address space is limited to 512Gb and LispWorks 6.0 reflected this, with the heap by default limited to around 160Gb. Newer Linux systems have a much larger address space and LispWorks 6.1 exploits this by adjusting its range to 4Tb.
For more details see the "Heap size" section in the "64-bit LispWorks" chapter of the LispWorks User Guide and Reference Manual .
LispWorks Release Notes and Installation Guide - 23 Dec 2011