Help With an Erastz-11 DLL

Can anyone help me with a simple link to an assembler / linker for a Pentium III / Pentium 4? I am attempting to use the EMEM.DLL (Emulated PDP-11 Memory) under Ersatz-11, but I am basically a dummy when it comes to using X86 code, especially finding a pair of suitable assembler / linker programs. I downloaded the Watfor programs, wasm.exe and wlink.exe, but I am not able to assemble the original file, EMEM.ASM at this point. In case anyone is interested, the EMEM.DLL under E11 provides access to PC RAM via emulated PDP-11 hardware registers. The current version which I have been using allows up to 8 MBytes, but I want to increase that to about 600 MBytes so that I can write a faster sieve program for Prime Numbers which looks like it runs in a PDP-11. If I can get the test version to run fast enough on a Pentium III, I will try it on a Pentium 4 with 4 GBytes of memory and see if it is possible to sieve the primes up to 10**18 (essentially a 64 bit sieve program) in a reasonable time (i.e. less than 1 year!).