I found an old Smalltalk/V imagine from 2000 and tracked down how I was able add calls to Windows DLLs and to add my own. It was in the class DynamicLinkLibrary and its subclasses, e. g., a call to the GDIDLL to draw a Bezier spline (which I believe I added) was: bezierTo: hDC lpPoints: anLPPOINT count: anInt <api: PolyBezierTo ulong struct ulong boolean> ^self invalidArgument I added by own DLL to do matrix transformations that was written in ASSEMBLER to optimized the floating point processor pipelining (a start operation every cycle while it took 3 cycles to complete) and it performed about 15% better. I have not found anything similar in Pharo, but it must if external libraries are used. NativeBoost seems to come close, but I cannot find any documentation. Can someone point me to some documentation, code, anything? It is greatly appreciated. bw