I finally managed to pull the contents out of the U6 (24LC256) EEPROM, the little 8-pin chip sitting right next to the USB port on the Line 6 HD500 Main Board (35-00-0386-1).
What it does
The CY7C68013A (EZ-USB FX2LP) is a USB microcontroller from Cypress. On power-up it has no firmware in ROM – it needs code to be loaded either from the host PC or from an external I²C EEPROM.
In the POD HD500, that code lives in the 24LC256. This EEPROM holds the firmware that configures the USB controller: USB descriptors, endpoint setup, and any custom routines the Line 6 engineers built in. Without it, the device would just enumerate as a generic Cypress USB controller. With it, the FX2LP comes up as a Line 6 POD HD500, ready to handle streaming and control messages.
You can grab the dump here (zipped BIN + CRC32):
