Welcome to the Xiaomi Mi MIX FAQ
This information has been gathered from various sources.
Any Additions/errors/corrections, please contact chodthewacko on XDA Forums.
Information in this document can become outdated as tools/roms/etc change to new versions.
You take responsibility for anything you do to your own phone!
Please verify correctness of any actions and make backups.

Table of contents:

  1. Mi MIX overview
    1. What is the Xiaomi Mi MIX?
    2. MIX Specifications
    3. Where can I get the phone?
    4. Will this phone work in my country?
    5. What language options are in the stock ROM?
    6. How did Xiaomi fit in such a large screen?
    7. How Fragile is this phone?
    8. How is the battery life?
  2. Hardware notes
    1. Teardown video
    2. Screen specifications
    3. Information regarding the Cameras
    4. Information regarding the earpiece
    5. Information regarding the proximity sensor
  3. Software notes
    1. Where are the google apps?
    2. How do I stop MIUI killing certain apps
    3. Where do I get Xposed for MIUI?
    4. Troubleshooting Apps
    5. How to enable developer options?
  4. ROMS and flashing
    1. How do I tell which ROM I have?
    2. Where can I get official ROMS?
    3. How do I flash the ROM?
    4. How do I get/install TWRP?
    5. How do I unlock the phone?
    6. How do I root the phone?
  5. Some complaints to be aware of
    1. Google voice does not seem to be working
    2. Some users complain 'up' gestures are too sensitve, making it hard to just swipe notifications off to the side. (it keeps registering an up swipe)
  6. Problems/fixes
    1. Google downloads are slow
    2. Lastpass app fill popups aren't working

Xiaomi Mi MIX Overview

What is the Xiaomi Mi MIX?

The Xiaomi Mi MIX is Xiaomi's "Concept phone".
It is quite distinct from other phones as it has a very small top bezel,
similar to the Sharp Aquos Crystal. In addition, it has minimal size bezels.

As a result, it is able to contain a 6.4" inch screen in a phone not much larger
than many 5.7 inch phones.

MIX specifications

Basic specificatons:
CPU - Snapdragon 821 2.35 GHz
GPU - Adreno 530
RAM - LPDDR4
OS - MIUI 8 (Android 6.0 Marshmallow)
Screen - IPS LCD 6.4 inches FHD (2040 x 1080)
Camera - Rear: 16MP/F2.0; Front: 5MP.
Battery - non removable 4400 mAh, Quick Charge 3.0
Fingerprint Scanner
Weight - 209g (7.37 oz)
Dimensions: 58.8 x 81.9 x 7.9 mm (6.25 x 3.22 x 0.31 in)
SIM: Dual Sim (Nano sim)
3.5mm headphone jack
USB Type-C 1.0
Ultrasonic proxmity sensor behind screen

No external SD card slot.
No IR blaster

There are two variants: 4GB RAM + 128GB Internal, and 6GB + 256GB.

Where can I get it?

The phone is only officialy sold in China.
It is being called a "concept phone" and manufactured in small quantities (roughly 10K a month).
Xiaomi occasionally has flash sales but they sell out quickly. (seconds).
Generally people are buying them other internet sales sites.
Due to demand the asking price of the phone is much higher than the official price from the xiaomi store.

Be careful where you buy it from - Some stores are not including the case,
some are installing their own ROMs, and some are not shipping to their preorder lists unless you send them more money. (due to demand increasing prices).

Screen Specifications

The Mi MIX has a 6.4 inch 16:10 screen
The resolution is 2040x1080 (~362 ppi pixel density).

The screen is made by Sharp, and this shouldn't be a surprise since the
MIX resembles the Sharp Aquos Crystal. Note the screen aspect ratio is 17:9.
When viewing a 16:9 full screen movie, there will be unused space on the sides.
The equivalent 16:9 window is roughly 6.12 inch equivalent.
Generally the 'extra' space is used for the (optional) onscreen navigation buttons.

Xiaomi advertises the screen/body ratio as 91.3%.
This number is debated a bit as people are measuring differently.
I.e. do you include onscreen button area? How wide are the bezels?
Are the buttons part of the 'width'?

Regardless, it's a lot higher than most phones on the market.

Will this phone work in my country?

A list of frequency bands supported by the MIX:
2G bands GSM 850 / 900 / 1800 / 1900 - SIM 1 & SIM 2
3G bands HSDPA 850 / 900 / 1900 / 2100
4G bands LTE band 1(2100), 2(1900), 3(1800), 4(1700/2100), 5(850),
7(2600), 8(900), 38(2600), 39(1900), 40(2300), 41(2500)

If it's what your carrier uses, you should be fine.

What language options are in the stock rom?

The Stock Rom only contains English, Traditional Chinese, English, and Tibetian.

The International (EU) Rom may have more.

How did Xiaomi fit in such a large screen?

Something very notable is that the Xiaomi is able to fit a very large screen in what is still a somewhat pocketable camera.
If you compare it to the current largest Iphone, the comparison is:
iphone 7: 158.20 x 77.90 x 7.30 mm. 5.5 inch screen. Mi MIX: 158.8 x 81.9 x 7.9 mm. 6.4 inch screen. The larger screen can get fit in because:
1) The MIX is wider. It's wider than most phones on the market.
2) The side bezels are quite thin compared to most phones
3) The top bezel is the same thickness as the side bezels.
Things normally located in the top bezel are either behind the screen
(the earpiece and proximity sensor) or on the bottom bezel (the front camera)

How Fragile is this phone?

With the screen so close to most of the edges/corners, dropping the phone
is quite risky. There are several instances of cracked screens due to dropped phones.

Note the ceramic body, although very scratch resistant, is slippery.
Therefore it's recommended to put on the case to avoid possibly dropping it.

Due to very short supply, getting your phone (or parts) replaced will take forever!

Information regarding the cameras

The two camera models are the OV5675 (5 MP) for the front camera, and the 16MP ov16880 for the rear camera. Both are by OMNIvision.

The general consensus is that the cameras are okay at day, but
not particularly good at night. There is no stabilization.

Some users report better results using 3rd party camera apps which
implies that the stock camera app may overdo noise reduction and softens the image.

Information regarding the earpiece

One of the most interesting things about the phone is the earpiece.
It is normally in the top bezel, but the MIX doesn't really have one.
So instead of using a regular speaker, which would require a hole, the
MIX uses Cantilever Piezoelectric Acoustic technology.

Most phones vibrate a speaker and you hear it through a earpiece hole.
The MIX (kind of) uses the entire phone as the speaker and in effect vibrates
the entire phone. This is how the earpiece can hide behind the screen.

Normally you'd then press your ear on the phone (front or back) to listen.
It's possible to crank up the volume to hear it, but it's not recommended.
(just like a normal earpiece) Overall most reviewers say it works pretty well.
There are a handful of complaints that it's too quiet, and some note that
having a vibrating phone on your face is a little odd.

When you use the speakerphone it uses the normal speaker/microphone on
the bottom of the phone.

Information regarding the proximity sensor

The proximity sensor on most phones is an infrared sensor that requires a
hole in the top bezel. Having a minimal top bezel, the MIX uses an
ultrasonic sensor that sits behind the screen.

General opinion is that the ultrasonic sensor works as well as an infrared sensor.
It's also notable that the Mi MIX has excellent battery life which indicates
that using an ultrasonic sensor isn't a notable battery drain.

How is the battery life?

The battery is 4400 mah, fairly large.
Reviewers almost universally consider the battery life excellent.
Note by default MIUI will aggressively kill any background apps, but
even with this turned off battery life is quite good.

Software notes

Where are the google apps?

Since it's a chinese phone, no google apps are installed by default.
The EU rom has them built in, and some vendors are installing them onto the phones before shipping.

Google apps can be downloaded and sideloaded onto the phone, or
downloaded from the Xiaomi app store.

Suggested steps for Stock Chinese ROM:

How do I stop MIUI killing certain apps

Use any/all of these to prevent MIUI killing specific apps like Wechat
(or any other applications that push notifications):

Note that it shouldn't be necessary to turn ALL of these off, but it seems MIUI 8 is
bugged and turning off most/all is necessary. Consider it a checklist of things to try:

First check these:

Then do any/all of these settings for each app: App specific notes:
gmail - the one in google play seems to work better than the one in the mi store.

Where do I get Xposed for MIUI?

Here

Troubleshooting Apps

Note some Apps only work if you load via Amazon Appstore.
Check App permissions and enable any blocked permissions as they may be breaking the app.

Specific app notes:

  • How to enable developer options? Settings -> About phone.
    Tap 'MIUI version" 7 times

    ROMS and flashing

    How do I tell which ROM I have?

    Note if the ROM version has 5 digits, it is a Vendor ROM and you should probably verify there is no Malware on it.
    Example: MIUI Global 8.0.5.0.0

    Where can I get official ROMS?

    Chinese Roms, click here
    EU Roms, click here

    Note that neither ROM seems to be working 100% for everyone.

    How do I flash the ROM?

    Use either fastboot or Miflash.
    Fastboot instructions     here
    Miflash Version 6.8.30 can be downloaded here

    Where do I get TWRP? and how do I install it?

    Download it via the XDA post     here Notes:

    How do I unlock the phone?

    First of all, it's possible your phone is already unlocked. Check using these steps:     link

    Steps:

    How do I root the phone?

    You can do it by installing SuperSU through TWRP.
    See the TWRP installation page for details:     link

    Google downloads are slow

    Google settings are tied to Mi app Store settings.
    In the app store, under user account -> downloads -> (bird),
    turn off download accelerator which uses a China proxy.

    Lastpass app fill popups aren't working

    MIUI by default will disable popups.
    Enable via: settings -> permissions-> permissions -> Lastpass -> Display pop-up window