Where do BootRom and MB1 store in?

The document says “The NVIDIA® Jetson™ TX2 BootROM (BR) is hard-wired in the Tegra chip. It initializes the Boot Media and loads Microboot1 (MB1) from the Boot Media.”

When I flash tx2, the log shows "/tegraflash.py --chip 0x18 --applet “./32.2.1/Linux_for_Tegra/bootloader/mb1_recovery_prod.bin” --skipuid --cmd “dum”, and the option “–applet” means “to be sent to BootRom”.

(1) Where the bootROM is hard-wired in, EEPROM on tx2 module or some else?

(2) Is MB1 in boot Media, internal EMMC? Then what the “to be sent to BootRom” means?

(3) The ipc-unittest-main is between “MB2(TBoot-BPMP) Recovery done” and “Welcome to TBoot-CPU Recovery” in the serial log. What part of bootloader dose it belong to,

FYI, Please refer to the attach files.
Serial-COM9_0925_10-20-23_flash_eMMC_recovery.log (117 KB)
flash_emmc_generateImage.log (581 KB)

Please refer to this slides.

and I believe ipc-unittest-main is from tos.img.