Why Flash the BIOS?

The stock BC-250 BIOS is functional, but it hides a number of useful options. The modded BIOS is primarily used to:

• Enable dynamic VRAM allocation using a 512 MB setting that lets the system balance memory between CPU and GPU.
• Expose additional VRAM split combinations beyond the limited stock presets.
• Unlock the chipset configuration menu for advanced tuning and behavior control.

Fan control and basic options exist in both stock and modded BIOS. Overclocking is generally not performed through the BIOS on this platform and is outside the scope of this guide.

Available Modded BIOS Versions

Community builds of the BC-250 BIOS typically come in two main variants:

P3.00 Chipset Menu (Recommended)

• Based on an earlier but well-tested code base.
• Unlocks chipset options and VRAM allocation controls.
• Considered the default, “safe” modded BIOS for general users.

P5.00_clv (Advanced Users Only)

• Built on a newer stock BIOS code.
• Exposes nearly every hidden menu and debug option, including things like ReBAR.
• Much easier to misconfigure and potentially brick the board.
• Only recommended if you fully understand the consequences of changing low-level chipset settings.

Recommendation: Use the P3.00 chipset menu build unless you have a specific reason and the experience to run P5.00_clv safely.

Flashing Methods Overview

There are two practical ways to flash the BC-250 BIOS:

Method 1: USB Flashing (EFI Shell) — Recommended

• No special hardware required beyond a USB drive.
• Runs through the board’s own EFI shell.
• Fast and straightforward when the system still boots normally.
• Requires a full CMOS clear afterward.

Method 2: Hardware Programmer

• Used to recover a bricked board or to take full BIOS backups.
• Requires a CH347, Pi Pico (serprog), or similar SPI programmer.
• More technical and slower, but much safer for recovery.

Owning a hardware programmer before you start is strongly recommended. USB flashing is convenient, but if something goes wrong, you will need a programmer to recover the board.

Method 1: USB Flashing (EFI Shell)

This is the standard way to flash a working BC-250. The idea is to boot the board into an EFI shell from a USB drive and run a provided script that handles the flashing.

Prerequisites

• USB flash drive, formatted as FAT32 (up to 32 GB recommended).
• BC-250 that can power on and display video.
• Display connected directly via DisplayPort where possible (HDMI adapters can cause BIOS black screens).

USB Flashing Steps

Step 1 — Download Required Files

1. Flashing tools (EFI kit)
   Download:
   4U12G BIOS Update.zip
   • Contains AfuEfix64.efi, Flash.nsh, and related utilities.
   • Also includes a stock P5.00 BIOS image — you will not use that for the modded flash.
2. Modded BIOS image
   Download from:
   TuxThePenguin0 GitLab – bc250-bios
   • Recommended file: BC250_3.00_CHIPSETMENU.ROM

Step 2 — Prepare the USB Drive

1. Format the USB drive as FAT32.
2. Extract 4U12G BIOS Update.zip.
3. From the extracted content, copy everything from the BIOS EFI folder to the root of the USB drive.
4. Move the included Robin5.00 (stock file) somewhere safe off the USB drive so you do not accidentally flash it.
5. Copy your modded BIOS file (for example, BC250_3.00_CHIPSETMENU.ROM) to the root of the USB.
6. Rename the modded BIOS file to:
   Robin5.00
   (no .rom extension)

After this step, the root of the USB drive should contain at least:

• AfuEfix64.efi
• Flash.nsh
• amdvbflash.efi
• Robin5.00 (your renamed modded BIOS)
• EFI/ directory

Step 3 — Boot from the USB into EFI Shell

1. Shut down the BC-250.
2. Disconnect all system drives (SSD, HDD) so the board cannot find an OS.
3. Insert the prepared USB drive.
4. Power on the board.
5. With no OS drives present, the system should automatically fall back to the EFI shell on the USB. You will see a yellow text prompt such as:
   Shell>

Step 4 — Run the Flash Script

1. At the Shell> prompt, select the USB device:

   blk0: 

   Note the space after the colon.
2. Run the flashing script:

   Flash.nsh

3. The AMI Firmware Update utility will start. Do not press keys, reset, or power off while it is writing. A flash that appears to pause can still be working; allow plenty of time.
4. When the process completes, the utility will report success and the board will either reboot automatically or prompt you to reboot.

Step 5 — Power Down and Remove USB

1. As soon as the flash is finished and the system begins to reboot, power the BC-250 off.
2. Remove the USB drive so it does not re-enter the flash script on the next boot.

CMOS Clear (Required After Flash)

Clearing CMOS after flashing is not optional. Without a proper CMOS clear, VRAM and chipset settings often fail to apply correctly and you may see inconsistent behavior.

Option A — Remove CMOS Battery

1. Disconnect power from the BC-250.
2. Remove the CMOS battery (CR2032) from the board.
3. Wait at least 60 seconds.
4. (Optional) Press the power button several times to discharge any remaining charge.
5. Reinstall the battery.

Option B — Use CMOS Jumper

1. Disconnect power from the BC-250.
2. Locate the CMOS clear jumper on the motherboard.
3. Move the jumper to the clear position for about 20 seconds.
4. Move the jumper back to the normal position.
5. Reconnect power.

Post-Flash BIOS Configuration

After clearing CMOS, you can power the system on and configure the new BIOS:

1. Power on the BC-250 and repeatedly press Del to enter the BIOS setup.
2. Go to Chipset → GFX Configuration:
   • Set Integrated Graphics Controller to Forces.
   • Set UMA Mode to UMA_SPECIFIED.
   • Set UMA Frame Buffer Size to 512 MB (recommended dynamic behavior) or your chosen fixed size.
3. Go to Advanced → CPU Configuration:
   • Set IOMMU to Disabled (unless you have a specific need for it).
4. Press F10 to save changes and exit.

Method 2: Hardware Programmer (Recovery and Backup)

A hardware programmer talks directly to the BIOS flash chip over SPI. This is the method you will use to recover a bricked board, or to take clean backups of the factory firmware.

Important Warnings

• Voltage: Many cheap black CH341A programmers output 5 V even when “set” to 3.3 V. The BC-250 flash chip requires 3.3 V. Always verify that your programmer truly uses 3.3 V logic.
• Two different flash chips: The board includes:
  • BIOS_A1 — 16 MB system BIOS. This is the chip you want.
  • SIO1_R — 512 KB Super I/O firmware. Do not write to this chip.
• If in doubt, stop: Writing to the wrong chip or at the wrong voltage can permanently damage the board.

Hardware Flashing Steps (Summary)

Tools and Hardware

• Programmer: WCH CH347 (recommended) or Raspberry Pi Pico running serprog firmware.
• Dupont jumper wires or an SOP8 test clip.
• A PC or laptop running Linux with flashrom installed.

Preparation

1. Unplug the BC-250 from the wall.
2. Press the power button a few times to discharge remaining power.
3. Connect the programmer to the BIOS_A1 chip via the J4004 header or a clip, observing proper pin orientation.

Flashrom Commands (Linux)

1. Install flashrom

sudo apt install flashrom

2. Detect the chip

Example for CH347; replace the programmer string as needed:

sudo flashrom -p ch347_spi

You should see a 16 MB part identified (for example, Winbond W25Q128 or Macronix MX25L128). If you see a 512 KB part, you are on the wrong chip.

3. Make a backup

sudo flashrom -p ch347_spi -r backup_stock.bin
sudo flashrom -p ch347_spi -r backup_verify.bin
diff backup_stock.bin backup_verify.bin

Only proceed if the two backup files match. Keep this backup safe in case you ever want to restore the original BIOS.

4. Write the modded BIOS

Place your chosen modded BIOS (for example, BC250_3.00_CHIPSETMENU.ROM) in the working directory, then run:

sudo flashrom -p ch347_spi -w BC250_3.00_CHIPSETMENU.ROM

5. After flashing

1. Disconnect the programmer and reconnect power to the BC-250.
2. Perform a full CMOS clear (see the CMOS Clear section).
3. Enter the BIOS and apply the VRAM and chipset settings from the Post-Flash BIOS Configuration section.