How to find system bios address in linux

I want to do some interaction with bios of a embedded linux on an AMD Ryzen embedded platform. The main tool I think is flashrom which can read/write flash chips. It should also be possible to write data to flash rom using something like dd if the address of the chip in memory is known? Is this the correct way to look for system bios: root@device:~/bios# grep ROM /proc/iomem 000c0000-000cd3ff : Video ROM 000f0000-000fffff : System ROM If I look for the rom using flashrom tool I get the following: root@device:~/bios# flashrom -p internal --flash-name flashrom v1.2 on Linux 5.4.199 (x86_64) flashrom is free software, get the source code at https://flashrom.org Using clock_gettime for delay loops (clk_id: 1, resolution: 1ns). Found chipset "AMD FP4". Enabling flash write... OK. Found Winbond flash chip "W25Q64.W" (8192 kB, SPI) mapped at physical address 0x00000000ff800000. vendor="Winbond" name="W25Q64.W" So the iomem says the chip is at 000f0000-000fffff and flashrom is saying he chip is at 0x00000000ff800000 Which one is correct, or better yet, why these are not identical?