PPC ROM

[Garth Wilson]

Get Diego's NoV-64 module instead, and then you can download images of lots of ROM modules into it, all for a lot less than the price of a single PPC ROM module.
http://www.clonix41.org/Projects/Nov64/Nov64_00.htm
His front page is http://www.clonix41.org/

If you have a coconut 41 (as opposed to a halfnut), you can use the 41CL transplant board that comes with something like 180 modules built in, and goes up to 50 times as fast as the original.
http://www.systemyde.com/pdf/sy41cl.pdf
http://www.systemyde.com/pdf/newt.pdf
http://systemyde.com/hp41/
http://www.wiki4hp.com/doku.php?id=41cl:..._cpu_board

There are modern module images you can put in it too, ones that have just come out in the last couple of years; so the 41 is still very much alive. Check out for example:
Ángel Martin's 41z module (.pdf) for true 4-level complex stack and tons of complex-arithmetic functions and enhancements, and
Ángel Martin's Sandmath module (.pdf) with gobs of math extensions for the HP-41