This is the range of fixnums in bits for the 32-bit builds of 39 Schemes. For this purpose, an exact integer n is a fixnum if n satisfies the implementation's fixnum? procedure (marked by an asterisk) or if there is no such procedure, then if (eq n n) returns #t.
31 bits: Racket*, Chicken*, Ypsilon*, Elk
30 bits: Gambit* , Scheme48/scsh, Guile, Chibi, Chez*, SCM, Ikarus*/Vicare*, Larceny*, Ypsilon*, Mosh*, IronScheme* (but see below), STklos*, RScheme*, Oaklisp*
29 bits: Gauche*, Bigloo*, SigScheme
26 bits: MIT*
16 bits: Owl Lisp*
9 bits: Scheme 7
No fixnums (even (eq? 0 0) is #f): SISC, KSi, TinyScheme, Scheme 9, Dream, BDC, UMB
Apparently unbounded fixnums: Shoe, Schemik, VX
Answer not easily determined: NexJ, XLisp, rep
In Kawa and IronScheme all exact integers are boxed, but a short range is preallocated, so that eq? is satisfied: -100 to 1024 for Kawa, -100 to 999 for IronScheme.