Posts: 887
Threads: 9
Joined: Jul 2007
+1 for the NoV-64! You can buy one modern module and have the ROM images of several older ones loaded into it. There are some modern module ROM images you'll probably want to load into it too, like the 41Z which gives your 41 a true 4-level complex stack and oodles and oodles of complex functions written in assembly (so they're much faster than user language), and the Sandmath module. See:
http://www.clonix41.org/Projects/Nov64/Nov64_00.htm
http://hp41.claughan.com/file/41Z_Manual.pdf
http://hp41.claughan.com/file/SANDMATH_44%20Manual.pdf
and you'll also be interested in the 41CL board transplant which makes the 41 up to 50x as fast and comes with something like 180 modules built in: http://www.systemyde.com/pdf/sy41cl.pdf