Just another quick note:

The assembler, first version is created. It seems that it outputs good machine code in hex, which can be then imported into ROM of the simulated computer.

It is not very sophisticated, just converts mnemonics into machine code; there is no support for directives and labels yet.

The source code, compiled binary for Windows, .bat file with commands for compilation of source with g++ and test file are in archive in "Files" section.

On another hand, work on making instruction cycles shorter encountered some problems -- it turned out much more work is needed than I thought at first. For now my attempts were hindered by data/clock races -- next instruction fetches and starts to execute while previous is still in progress, or bus congestion occurs.