I believe that the command which retrieves the chip ID fails and "01 20" isn't the actual ID but some data from the ROM. Hopefully the chip doesn't require 12v to page-write...
Workarounds :
A -
Build an installer EXE (EXPAND.EXE) from the .rom file, using no$psx v2.0.
rama3 wrote:[...]
Got it working!
I loaded PSX-EXP.ROM into no$psx and then choose the menu option 'Create currently loaded expansion rom installer (EXPAND.EXE)'.
This executable worked in no$psx so I burned it to CD and it booted up on real hardware.
It detected my Xploder just fine and installed to it!
nocash wrote:Installer EXE
[...]
1) Create nocash expansion rom as raw image (PSX-EXP.ROM)
2) Load PSX-EXP.ROM via "cdrom" filemenu (this will internally allocate 20000h bytes for it, fixing the issue)
3) Create currently loaded expansion rom installer (EXPAND.EXE)
The third step was normally intended for third-party roms (like datel/caetla/xplorer firmwares, for cases when existing burning tools don't work with certain chipsets, like the xplorer carts with two flash chips in them).
... where PSX-EXP.ROM is the standalone UniROM .rom file.
B - If the above did not work, use the hexhacked X-Flash of
Cheat Engine Compilation, at your own risk.
That mod forces the flashing of "unknown" EEPROMs with default parameters and
may brick the cartridge in the end. Very unsafe. If it goes wrong and corrupts the contents, a hardware programmer will be needed to rescue it.
Steps are :
1) Run the disc and select "X-Flash Overburn Mod", it's the last item of page 3/3;
2) Choose "Development Stuff", then "128 Bytes Sector + ROMFILE.DAT";
3) Go to the X-Flash ROM list and pick one of the standalone builds of UniROM (without Caetla);
4) Reboot.
https://youtu.be/5Z6e1HJTjyU
Again, this method is risky and could ruin your fake GameShark cartridge.