file   : readme.txt
author : MetalliC
created: 2022-10-18

at 1st sight it was not really interesting cart, because of missing program ROM and game data almost same as official release, but IC20 was a bit of surprise - it was identified as NAOMI development box BIOS ROM, and until this day we had none of them dumped.
someone may notice - but in naomi.cpp we already have few "Dev BIOS"es, right, but they are very special tools for hardware testing, serial EEPROMs programming, ROM board copying and other such tasks, but not BIOSes for game debugging and development purposes.

there is only 1st half of BIOS but it's not big problem because missing 2nd half contain only part of gfx assets (fonts etc), so it's possible to simply append it from other rev A BIOS and will be enough for emulation or research purposes (but not for use on real hardware, because of CRC protection)

that's the difference with regular BIOS ?
- enabled monitor/debugger.
this BIOS ROM does read DIP switches of dev.rom board and depending on SW8 will do normal boot or wait for commands from remote debugger. other switches set type of communication - SCSI (common way), UART or SH4's SCIF.
if no dev.board was detected BIOS will default to SCIF comms and debugger mode enabled (i.e. on regular NAOMI it will "hang" and wait for debugger commands via SH4's SCIF serial port)
a bit interesting part - all the retail BIOSes still have that debugger routine and run it at very early boot stage, but have it kind of hardcoded to "normal boot" mode instead of read DIPSW, so they immediately jump out of debugger. 
- BIOS region not hardcoded but read from mobo SW2-4
it seems all the differences, not much but still quite interesting, and in theory makes possible to do some game dev using NAOMI SDK and dev.rom board