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HOW CAN I PUT CUSTOM ROMS FOR GALAXY A90?

How can I put custom roms for galaxy a90?

Understanding The Samsung Galaxy A90 5G (SM-A908) Architecture

In our extensive experience with Android modification, we have identified the Samsung Galaxy A90 5G (model number SM-A908B/DS, SM-A908U, etc.) as a unique device in the Samsung ecosystem. Unlike many of its contemporaries that utilized the Exynos chipset, this device is powered by the Qualcomm Snapdragon 855 processor. This distinction is critical when attempting to flash custom ROMs. The architecture dictates the tools required and the specific steps necessary for a successful modification. When we approach the Galaxy A90, we are dealing with a Qualcomm SoC (System on Chip), which utilizes the ABOOT and EL2 partitions for the boot chain.

This hardware foundation is the primary reason why generic tutorials often fail. A user searching for guidance might stumble upon videos showing “blue screens with Korean texts.” This specific visual error is almost exclusively associated with Samsung’s Download Mode (Odin Mode) throwing a Samsung Safety Violation error. In our analysis, this occurs because the bootloader on the Galaxy A90 is tightly locked to the specific region and carrier firmware. Attempting to flash a binary intended for a different model (like the Galaxy A90 5G vs. the LTE variant) or using an incompatible BL (Bootloader) file will trigger this safety mechanism.

Furthermore, a common misconception we must address immediately is the question: “Can I put Pixel ROMs into this?” The answer is nuanced. While the Galaxy A90 has excellent developer support, you cannot simply take a generic Google Pixel Experience ROM designed for a Pixel device and flash it. You must use a custom ROM specifically built for the SM-A908 hardware. These ROMs are essentially “ports” or “builds” that adapt the Android Open Source Project (AOSP) or Pixel software to function on Samsung’s specific hardware drivers (blobs).

Prerequisites for Flashing Custom ROMs on the Galaxy A90

Before initiating any modification to the system partition, we must prepare the environment meticulously. The process relies heavily on Unlocking the Bootloader, which is the gatekeeper of the device’s security. We strongly advise backing up all critical data. Unlocking the bootloader on a Samsung device via the OEM Unlocking toggle in Developer Options will trigger a factory reset. The device will wipe all user data to ensure no compromised data remains on a device with an unlocked chain of trust.

We categorize the necessary tools as follows:

It is vital to ensure the device has sufficient battery charge, ideally above 60%, to prevent a shutdown during the flashing process, which could result in a hard brick.

Addressing The “Blue Screen with Korean Texts” Error

We understand that encountering a Blue Screen with Korean text during the modification process is alarming. In our technical documentation, this screen is referred to as the “Secure Download Mode” or a “Knox Warranty Bit” violation screen. It is distinct from the standard black Download Mode. This usually happens for two reasons in the context of the Galaxy A90:

  1. Incorrect Firmware Combination: You may be attempting to flash a PIT (Partition Information Table) file or a firmware binary that does not match the device’s region or hardware revision. The Samsung bootloader verifies the header of the binary. If the hash or the model ID does not match, it halts and displays this screen.
  2. Knox E-Fuse Triggered: Samsung has a physical fuse (e-Fuse) that counts the number of times the bootloader has been modified (tripped Knox). Once tripped, certain enterprise features are disabled. However, a blue screen during Odin flashing usually indicates a blockage by the RMM (Remote Monitoring and Management) or KG (Knox Guardian) status.

The Solution: To bypass this, we must ensure we are flashing the correct BL (Bootloader) and AP files. If the device is stuck in this mode, you must force restart by holding Power + Volume Down. If the “OEM Unlocking” toggle was enabled in the developer menu before the issue occurred, you can usually re-enter Download Mode and flash a stock firmware to recover. If OEM Unlocking was not enabled, the device is effectively locked into a “KG Locked” state, which requires waiting for a specific timer (often 72 hours to 168 hours) before the toggle becomes active. This is a security feature to prevent theft.

Unlocking the Bootloader on the Samsung Galaxy A90

To proceed with custom ROM installation, we must unlock the bootloader. Follow these steps precisely:

  1. Navigate to Settings > About Phone > Software Information.
  2. Tap on Build Number seven times to enable Developer Options.
  3. Go to Developer Options and enable OEM Unlocking. This is the most critical step. If this toggle is grayed out, it indicates the device is locked by a carrier or RMM state, and you cannot proceed until that state is cleared.
  4. Power off the device completely.
  5. Press and hold Volume Up + Volume Down and connect the USB cable to your PC. This forces the device into Download Mode (Odin Mode).
  6. Press Volume Up to confirm the unlock.
  7. The device will reboot and perform a factory reset. You will see a warning message on the boot screen indicating “Orange State” or “Bootloader Unlocked.” This confirms you are ready for the next phase.

Installing a Custom Recovery (TWRP) via Odin

Since the Galaxy A90 uses a System-as-Root structure (A/B partitioning), the method of installing recovery has evolved. We will use Odin to flash TWRP. However, you cannot flash a standard TWRP .img directly and expect it to stick because Samsung’s stock ROM overwrites the recovery partition on every boot.

Instead, the community developed a solution involving a Patched Boot Image or flashing a TWRP Installer via Odin. For the Galaxy A90, we recommend the following approach:

  1. Download the TWRP Recovery image specifically for the SM-A908B.
  2. Rename the file to recovery.img.
  3. Open Odin3 on your PC.
  4. Click the AP button (or User Lock in some older Odin versions) and select the recovery.img file.
  5. Crucial Step: In Odin, go to the Options tab and check Auto Reboot.
  6. Connect the phone in Download Mode.
  7. Click Start.

Note: On some Samsung devices, simply flashing recovery via Odin is not enough because of Force-Onedex encryption. You may need to use a tool like Frija to download the exact stock firmware, extract the boot.img.lz4, patch it with Magisk, and flash that via Odin to achieve root and recovery capabilities simultaneously.

If Odin fails or the recovery gets overwritten, we must use the “Disable Dm-Verity Force Encrypt” patch or flash vbmeta to disable verification. We often flash vbmeta.img with the command --disable-verity --disable-verification to prevent the system from checking the integrity of the recovery.

Flashing the Custom ROM for Galaxy A90

Once we have a working custom recovery (TWRP) or a rooted boot image, we can proceed to flashing the custom ROM. To answer the question regarding Pixel ROMs: You cannot flash the official Pixel ROM. You must look for community builds such as LineageOS, Pixel Experience (Port), or Project Elixir specifically compiled for the qcom/sm8150 platform (Snapdragon 855).

The Procedure:

  1. Download the ROM Zip: Ensure the file matches your exact model (SM-A908). The file size is usually large (1GB+).
  2. Transfer to Device: Move the ZIP file to your internal storage or an SD card.
  3. Reboot to Recovery:
    • If you have TWRP installed: Hold Volume Up + Power until the Samsung logo appears, then release Power but keep holding Volume Up until TWRP loads.
    • If you are using a Magisk-patched boot image: You can use the “Reboot to Recovery” option inside the Magisk app.
  4. Wipe Data: In TWRP, select Wipe > Format Data. Type yes to confirm. This is required because Samsung’s encryption will prevent the new ROM from reading the data partition. Do not just wipe cache/dalvik; you must format data to remove encryption.
  5. Wipe System/Vendor (Optional but Recommended): Go to Advanced Wipe and select System, Vendor, and Data. Swipe to wipe.
  6. Install the ROM:
    • Go back to the main menu and select Install.
    • Navigate to the ROM ZIP file.
    • Swipe to confirm flash.
    • Wait for the installation script to complete. The script will automatically install GApps if the ROM is “GApps Ready,” or you may need to flash a separate OpenGApps or NikGApps package immediately after the ROM (before the first reboot).
  7. Install Magisk (Optional): If you want root, flash the Magisk ZIP or the Magisk.apk renamed to .zip immediately after the ROM installation.
  8. Reboot System: This first boot may take 10-15 minutes. Do not interrupt it.

Troubleshooting Bootloops and “Blue Screen of Death”

If the device fails to boot (Bootloop) or returns to the Blue Screen, we must troubleshoot systematically.

The “Verity” Issue: The most common cause of bootloops on the Galaxy A90 after flashing a ROM is AVB (Android Verified Boot). The bootloader detects that the system or vendor partition has been tampered with and refuses to boot. To fix this, we must flash a vbmeta disabler.

Recovery Steps:

  1. Download vbmeta.img (disabling verification).
  2. Reboot to Download Mode.
  3. Open Odin.
  4. Put the vbmeta.img in the AP slot.
  5. Important: In Options, check Nand Erase All (only if you are recovering from a hard brick, otherwise leave unchecked) or simply Auto Reboot.
  6. Start the flash.
  7. If this succeeds, the device should boot with verification disabled.

Handling “Knox Warranty Bit” Errors: If you see a message saying “Knox Warranty Bit: 0x1” or similar, this is permanent. It means the warranty is void, but it does not prevent the device from booting. However, if the device says “Prenormal” or “RMM Prenormal,” the device will not boot custom ROMs until the RMM state is cleared. This usually requires flashing stock firmware, re-enabling OEM unlock, and waiting 72 hours while the device is connected to the internet. This is the notorious RMM/Prenormal lock.

Can You Install Pixel ROMs (Pixel Experience) on Galaxy A90?

We return to the specific query about Pixel ROMs. While we cannot flash the official Pixel firmware built for Google devices, the Android modding community has ported the Pixel Experience and PixelOS to the Galaxy A90. These are not “official” but are highly stable.

The Difference:

When downloading these, look for the specific tag “raphael” (Snapdragon 855 generic) or specific “starqlte” (Samsung specific) support. For the Galaxy A90 5G, the device codename is “A908” or “RP1” (depending on the specific network variant). Ensure the ROM thread explicitly states “SM-A908B” support. If you flash a ROM for the SM-A908U (US model) on an SM-A908B (Global model), the modem may not work, resulting in no cellular signal.

Post-Installation: GApps and Root

After successfully flashing the custom ROM, the device will boot into a clean Android environment. Most custom ROMs do not come with Google Apps pre-installed due to licensing issues (except for specific “GApps” builds).

Installing GApps:

  1. Download OpenGApps (Arm64, Android version matching your ROM, Micro/Pico variant recommended to avoid bloat).
  2. Flash the ZIP in TWRP immediately after the ROM (before the first reboot if possible, or after if you forgot).
  3. Reboot.

Rooting with Magisk:

  1. Download the Magisk APK from the official GitHub.
  2. Rename the file from app-release.apk to Magisk.zip.
  3. Flash this in TWRP.
  4. Alternatively, patch the boot.img from your ROM’s factory image using the Magisk app and flash it via Odin in the AP slot.

Summary of Risks and Recommendations

We must conclude by emphasizing the risks involved in modifying the Galaxy A90. The “Blue Screen” is a protective measure. To avoid it, strictly adhere to model numbers. Do not attempt to flash LTE-only firmware on a 5G model or vice versa.

Always verify the RMM State before attempting to flash. If the RMM state is “Prenormal,” the flash will fail. The device must be “Normal” or “Unlocked.” If you are currently stuck on a Blue Screen with Korean text and cannot access Download Mode, you must force a restart into Download Mode. If that fails, you may need to use a USB Jig (a specialized hardware tool) to force the Galaxy A90 into Download Mode, bypassing the software lock. However, USB jigs are rare and specific to certain charging port behaviors.

By following this comprehensive guide, utilizing the correct TWRP, disabling verification via vbmeta, and choosing the right custom ROM build for the SM-A908, you can successfully transform your Samsung Galaxy A90 5G into a pure Android powerhouse, free from Samsung’s heavy software layer.

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