I ve added another article: Pinczakko s Guide

I've added another article:
Pinczakko's Guide to Self-patching Expansion ROM Source Code

This article explain how you can build an ISA expansion ROM with Fasm without having to take care of the checksum and let Fasm patch the checksum automatically in your expansion ROM source code.

The technique is easily extended for PCI expansion ROM development. However, due to lack of time. I don't present it there. You can figure it out easily yourself

Anyway, you'd better read flat assembler 1.66 user manual section 2.2.4. If you are confused with the use of the preprocessor in the article