FreeWare Scheme - IBM PS/2 or AT

[STCS8004%IRUCCVAX.BITNET@MITVMA.MIT.EDU]

I wish to teach Scheme to 2nd and 3rd Honours CS students and
would like to distribute a Shareware/Freeware version to them for
use on IBM PS/2 1mB+HD and Unisys Micro IT 640kB+HD.  Full Scheme
is not essential - a viable subset is quite sufficient.  I have a
small subset implemented as an interpreter running under PCLisp
(subset Franz) broadly modelled on Abelson and Sussman, but this is
far too slow and lacks diagnostics at the Scheme level.  Information
on what is available free would be most welcome.       G. Oulsnam.