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BC-250 BIOS Reader

Reads the BIOS settings of the AMD BC-250 on Bazzite and shows them in a layout like the BIOS setup screen, hidden menus included. It only reads: nothing on the board or in the BIOS changes.

It also tells a stock BIOS from a modded one and says what gave it away.

Using it

The window opens on this board: the setup screens of its BIOS release and the values Linux can read.

  • Tabs: Main, Advanced, Security, Boot, Save & Exit, then the pages other BIOS modules add (AMD CBS, network, recovery). Left and Right switch tabs.
  • Items: Up and Down select, Enter opens a submenu, Esc goes back. The right side shows the item's help, its value and default, its options and where it is stored (for example AmdSetup + 0x25F, 4 bytes).
  • Show hidden items (or H): also lists what the BIOS does not show, in gray italics, with the reason: hidden always, hidden by the value of another setting, or a menu no link leads to. The extra Not linked tab opens the menus that no menu links to.
  • The status next to the title: Stock BIOS or Modded BIOS. Hover it to see why.
  • Read BIOS chip…: reads the flash chip and opens the dump. See below.
  • Open dump…: opens a BIOS image made earlier. This board goes back to the running board.

What this board shows without a dump

Linux can read only the UEFI variables the BIOS leaves visible after boot. On the BC-250 that is AmdSetup, the AMD CBS settings, so those show their real values. The main Setup variable (the Main, Advanced, Chipset and Boot options) is hidden after boot: those options show [?], and their help shows the default. A dump of the flash chip has both.

The setup screens themselves come from a table built into the app, one per known BIOS release (P5.00). For another release, read the chip: the app then reads the screens from the dump.

Where the settings come from

The BC-250 runs an AMI Aptio BIOS. Its settings are stored as UEFI variables in the NVRAM part of the BIOS flash chip.

Variable What it holds Readable from Linux
AmdSetup the AMD CBS options (CPU, memory, GPU) yes, /sys/firmware/efi/efivars, no root needed
Setup the main Aptio options (Advanced, Chipset, Boot) no, the BIOS hides it after boot; only in a flash dump
StdDefaults the default values only in a flash dump
AMITSESetup settings of the setup screen itself only in a flash dump

A variable is just bytes. The names, allowed values and menus of the options are stored as forms (HII/IFR) inside the BIOS image. These forms map each byte in Setup or AmdSetup to an option such as "UMA Frame Buffer Size". They also hold the conditions under which the setup screen hides an option or a menu, which is how the app knows what is hidden.

Reading the BIOS flash chip (optional)

You decide whether to make a full dump of the flash chip. The app works without one. Reading is safe: flashrom only reads with -r, and the app never runs it otherwise. Never run flashrom with -w or -E yourself.

The BC-250's BIOS sits on a Winbond W25Q128.V (16 MiB, SPI) behind the AMD FCH.

Getting flashrom

Homebrew's flashrom has no internal programmer, so it cannot read the board's own chip. Fedora's package can. Unpack it into a folder of your own instead of layering it onto Bazzite:

mkdir -p ~/flashrom && cd ~/flashrom
dnf download flashrom.x86_64 libjaylink.x86_64
rpm -K ./*.rpm                      # signatures must be OK
for p in ./*.rpm; do rpm2cpio "$p" | cpio -idm; done

The app finds flashrom in ~/flashrom (and on the PATH).

From the app

Read BIOS chip… asks first, then runs flashrom twice through a password prompt and compares the two reads. The dump goes to ~/.local/share/bc250-bios-reader/dumps/ and opens right away. Uninstalling the app keeps the dumps; --purge removes them.

By hand

Probe first. This only detects the chipset and the chip:

sudo env LD_LIBRARY_PATH="$HOME/flashrom/usr/lib64" ~/flashrom/usr/bin/flashrom -p internal

Look for Found Winbond flash chip "W25Q128.V" (16384 kB, SPI). Then read the chip, twice:

sudo env LD_LIBRARY_PATH="$HOME/flashrom/usr/lib64" ~/flashrom/usr/bin/flashrom -p internal -c "W25Q128.V" -r bios.bin
sudo env LD_LIBRARY_PATH="$HOME/flashrom/usr/lib64" ~/flashrom/usr/bin/flashrom -p internal -c "W25Q128.V" -r bios2.bin
sha256sum bios.bin bios2.bin        # both must match

Two identical dumps mean the read is stable. Each ends with Reading flash... done. Open bios.bin with Open dump….

What flashrom prints on the BC-250, and why it does no harm:

  • No DMI table found and the laptop warning: flashrom cannot tell what kind of machine this is and turns off some buses to be careful. The BC-250 has no embedded controller (EC), which is what the warning is about, and the SPI bus it needs is still found. No laptop= override is needed.
  • Enabling flash write... OK: flashrom prepares the chipset as it always does. Nothing is written without -w.
  • /dev/mem mmap failed lines (probe without -c only): flashrom tries chip types larger than 16 MiB at addresses that are not flash on this board, and the kernel refuses them. Naming the chip with -c skips them.

A dump is your board's own firmware, with its settings. Keep it to yourself.

Unpacking a dump

The app unpacks a dump itself. To look inside one by hand: a dump is a 16 MiB image, most of it (about 80 %) empty (0xFF). UEFITool opens it; its command-line tool UEFIExtract unpacks it:

uefiextract bios.bin report     # bios.bin.report.txt: a list of everything in the image
uefiextract bios.bin all        # bios.bin.dump/: every volume, file and section as a folder

What is inside:

  • The NVRAM store (the first volume): every UEFI variable, Setup, AmdSetup, StdDefaults and AMITSESetup among them. A variable that was saved more than once is a chain of entries; the last one is current.
  • The firmware volumes: the BIOS code. The main volume is LZMA-compressed, so its text is not readable in the raw dump.
  • The setup modules in the firmware volumes hold the forms (IFR) and their strings (the option names in en-US). On the BC-250 these are Setup (the main menus) and CbsSetupDxe (AMD CBS), plus small ones for the network card, HTTP boot, NVMe, the Super I/O and recovery. IFRExtractor-RS turns them into readable text.
  • The SMBIOS data: the BIOS vendor, version and release date (American Megatrends Inc., P5.00, 05/03/2022).

Stock or modded

  • With a dump (certain): the app compares the setup screens in the dump with those of the stock release of the same version, byte for byte. A modded BIOS changes them to show hidden menus; the status then lists the changed screens and the menus stock hides that this BIOS shows.
  • Without a dump (a strong hint): the version string (a modded BIOS often says so), and the size of the AmdSetup variable, which changes when the AMD CBS screens are changed. Many modded BIOSes keep the stock version string, so only a dump proves a BIOS is stock.

Install

Install it from the BC250 Bazzite Suite portal, or from a clone or release folder, as your own user:

./install.sh                         # app menu entry and Desktop icon
./install.sh --no-desktop-shortcut   # app menu entry only
./install.sh --uninstall             # remove the app; keeps its settings and BIOS dumps
./install.sh --uninstall --purge     # also remove its settings and BIOS dumps

bc250-bios-reader --dump FILE opens a dump from the terminal. bc250-bios-reader --build-table DUMP makes the built-in table of a stock release from a dump of it.

License

GPL-3.0-or-later. See LICENSE.