The Mi MIX 3 (codenamed perseus) was Xiaomi’s innovative flagship featuring a magnetic slider mechanism, bezel-less display, and ceramic body design. If your device is experiencing slider mechanism issues, camera malfunctions, performance problems, or software instability, this guide provides the official MIUI fastboot ROMs and custom recovery needed for complete system restoration.

Important Notice: Verify your device codename is perseus before flashing. The Mi MIX 3 has unique hardware including the magnetic slider mechanism that requires specific firmware optimization. Flashing incorrect firmware will result in a non-functional device.

Quick Device Specifications

Device: Mi MIX 3 (perseus)
Release Year: 2018
Chipset: Qualcomm Snapdragon 845 (10nm)
Display: 6.39″ AMOLED, 1080 × 2340 pixels (19.5:9)
Camera: 12MP + 12MP dual rear (2x optical zoom), dual 24MP+2MP front
Battery: 3200 mAh with Quick Charge 4+
Security: Rear fingerprint scanner
Special Feature: Magnetic slider mechanism, ceramic body, bezel-less design
Original OS: Android 9.0 Pie, MIUI 10

Essential Downloads & Tools

File / Tool	Download Link
Xiaomi Mi Flash Tool	Download Stable Version
Qualcomm USB Drivers	Download Latest Drivers
TWRP Recovery	TWRP 3.3.2B for perseus
ADB and Fastboot Tools	Official from Google
Mi Unlock Tool	Bootloader Unlock

Official Fastboot ROM Collection

Region / Variant	Build Version	Android	Release Date	Download Link
China Stable	V12.5.1.0.QEECNXM	10.0	2021-07-04	Download
Global Stable	V12.0.2.0.QEEMIXM	10.0	2020-11-16	Download
TWRP Recovery	3.3.2B-0306	10.0	—	Download

Flashing Guide for Mi MIX 3 (perseus)

Method 1: Fastboot Flashing (Official)

Driver Installation: Install Qualcomm USB drivers on your computer.
Bootloader Unlock: Unlock bootloader using Mi Unlock Tool (requires waiting period).
Enter Fastboot Mode: Power off device, then hold Volume Down + Power buttons.
Flash Process:
- Extract the .tgz file to access firmware folder
- Open Mi Flash Tool and browse to extracted folder
- Select “Clean All” option for fresh installation
- Click “Flash” and wait for completion (5-7 minutes)
First Boot: Initial boot may take 5-10 minutes as system optimizes.
Slider Calibration: Calibrate the magnetic slider mechanism through hardware test menu.

Method 2: TWRP Recovery (Custom)

Flash TWRP: fastboot flash recovery twrp.img
Boot to TWRP: Hold Volume Up + Power during boot
Backup Partitions: Backup persist and modem partitions first
Install Custom ROM: Flash custom ROMs from storage
Wipe Data: Format data for clean installation

Frequently Asked Questions (FAQs)

Q1. Why is my slider mechanism not working properly after update?
The magnetic slider requires specific firmware calibration. Flash the stock ROM and recalibrate through hardware test menu (##6484## → Slider Test). This often resolves slider responsiveness issues.

Q2. Can I upgrade to Android 11 on Mi MIX 3?
No, Android 10 was the final official Android version. However, there are custom ROMs like Pixel Experience and LineageOS 18.1 (Android 11) available through TWRP if you unlock the bootloader.

Q3. Why is the China ROM version newer than the Global ROM?
Xiaomi typically provides longer update support for the Chinese market. The China variant received MIUI 12.5 with July 2021 security patches, while Global stopped at November 2020.

Q4. How can I improve battery life on my MIX 3?
The 3200mAh battery is relatively small for flagship usage. After flashing, calibrate the battery, use dark mode with the AMOLED display, and restrict background app activity.

Device-Specific Troubleshooting

Slider Mechanism: The magnetic slider requires specific calibration. Test slider functionality after flashing through hardware test menu.
Camera Performance: The dual 12MP rear and dual front cameras need proper calibration. Test all cameras after flashing.
Battery Optimization: The 3200mAh battery benefits from calibration after flashing. Use battery optimization features in MIUI.
Performance Management: The Snapdragon 845 is still powerful. Use Game Turbo for enhanced gaming performance.

TWRP Installation Guide

Unlock bootloader officially through Mi Unlock
Boot to fastboot mode: Power off → Volume Down + Power
Flash TWRP: fastboot flash recovery twrp.img
Boot to TWRP: fastboot boot twrp.img
Backup critical partitions: persist, modem, EFS
Format Data: Wipe → Format Data → type “yes”

Note: Always backup your persist partition before flashing custom ROMs to avoid slider mechanism and sensor issues.

Version Comparison Advice

China ROM (V12.5.1.0): Newest features, latest security patches (July 2021), but may contain Chinese apps and lack some Google services optimization.

Global ROM (V12.0.2.0): Better Google services integration, stable for international users, but older security patches (November 2020).