The two hex files found here are for the two different variants of the 
HCS II SC.  hcs-420-18.hex is for the upgraded HCS II SC boards with the 
Z80S180 CPU, while hcs-420-9.hex is for HCS II SCs using the original CPU.

host.exe and compile.exe will work with either ROM version.

You need an EPROM burner to write the Intel HEX format EPROM file.  Then,
power down, swap EPROMs (keep the old one in a safe place) and power up.
You'll need the host.exe and compile.exe programs for the matching ROM.

Documentation for this release is located in the /hcs/hcs-docs/ part of the
site.

Source code for the HCS II SC ROM is copyrighted, but placed under the GNU
GPL.

Questions about this release should be directed to the Circuit Cellar BBS.