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29.2 Heap size

In principle 64-bit LispWorks can grow to almost 16 TB but it is intentionally limited to a defined range in order to avoid clashes with other software as shown in Default range for 64-bit LispWorks heap.

Default range for 64-bit LispWorks heap


Default range


Intel-based Macintosh

#x4000000000 to #x40000000000 (3.75 TB)


PowerPC Macintosh

#x4000000000 to #x40000000000 (3.75 TB)


old Linux

#x4000000000 to #x7000000000 (192 GB)

Effective limit around 160 GB.

modern Linux

#x4000000000 to #x44000000000 (4 TB)



#x4000000000 to #x40000000000 (3.75 TB)



#x4000000000 to #x10000000000 (768 GB)


In contrast, 32-bit LispWorks has a maximum heap size of 1.5-3.0 GB depending on platform.

Normally 64-bit LispWorks for Linux automatically adjusts its default heap size on startup according to whether it runs on "old Linux" or "new Linux". On old systems, LispWorks sets the end of its range to x7000000000. On new systems, it sets the end to #x44000000000, thus giving a range of 4 TB. However, if the size is given explicitly by command line argument --reserve-size or InitLispWorks in a dynamic library, then this overrides the automatic adjustment.

LispWorks is relocatable on all supported platforms as described in Startup relocation of 32-bit LispWorks and Startup relocation of 64-bit LispWorks.

LispWorks User Guide and Reference Manual - 20 Sep 2017