Hello S?bastien, >From 20f onwards [1] we have: 'Support for x87 has been dropped (effective with the 2014-05 snapshot). All further releases will require an x86 chip that supports sse2. SSE2 was introduced with the Pentium 4 in 2001. ' So upstream doesn't handle non-SSE2 anymore, and amd64 isn't a supported architecture for CMUCL. SBCL took this role. Best regards, Peter 1 https://trac.common-lisp.net/cmucl/wiki/Release20f