Garmin Fenix 7X Solar Teardown (Non Destructive)


Sometimes you have an urge to consume some money. You simply want to burn it and then, you lose it. In the end, you’re with a toy that’s kinda same with an older model, but with some tiny differences and a few more installed games. 🙂 The worse is, you want to see what’s inside it. 😀 You start to prepare your tools; screwdrivers, tweezers, balls etc. etc…

Garmin Fenix 7X Solar.

New Fenix 7 and Epix series have four screws and they’re not on the bezel, but near the strap pins. This was needed to make the bezel thinner, so that they can increase the area of solar band inside the screen area. Also now the screws are smaller and in a smaller diameter. At first this design seemed less durable compared to older five screw design. Actually, I thought the bezel may not transfer enough force to the center (6 and 3 hours part) and this may decrease its water resistance under high pressure. However, once I removed the four screw and get the bezel part on my hands, it felt really solid and durable, not flexing etc. Still smaller screws near the pins makes me believe it’s not strong as the older models but I’m sure it’s strong enough. Anyway, it won’t be easy to destroy this. Glass is glass, but display of this watch seems more colour accurate compared to Fenix 6X Pro. However, sometimes reflections on it are a bit unpleasent. I think power glass has some layers under the glass and it gives some more reflectance to it, making it sometimes like a mirror or sometimes making it harder to see what’s on the display.

Garmin Fenix 7X Solar Display Module
Garmin Fenix 7X Solar Display Module

Behind the bezel, we kinda have the same 280 x 280 pixels display module. Now, the gasket around the bezel is blue instead of red. That gasket protects inside of the watch from water and sweat outside. We have two connectors coming from the display, which connects the display, solar cells, touchscreen surface and maybe NFC antenna to motherboard. Also there is and extension on the connection ribbon with a QR code on it. QR code contains some numbers etc… Probably some part codes.

Also around the bezel, there are lots of contact points. They must be GNSS antenna contacts. Yeah, it seems this watch has that Garmin’s EXO antenna thing, too.

Garmin Fenix 7X Solar inside the casing.

Put aside the bezel, and now we have the watch casing with a motherboard inside. Removing the motherboard is as easy as always. Just remove a few connecters and screws, and be careful doing that!!! Although battery is placed below the motherboard, it’s connector is above it, or in its front side. You just need to lift the part with cables from the exterior part. Not a hard job, but simply be careful, slow and think what you do and do it without damaging the connector. Later, you can unscrew the screws and remove the motherboard.

Under the motherboard.

Internal layout of Fenix 7 series is a bit different than the older series. Battery is glued to the case, instead of the motherboard. And it’s glued well. If you need to change it, be careful not to destroy other parts while doing it.

By the way, battery is 534mAh and 2.06Wh. It’s Garmin labelled, but manufactured by Dongguan Amperex Technology Limited. Looking at production date it was ten months old when the device was bought.

Garmin Fenix 7X Solar vibration motor.

Vibration motor is round now and placed near the battery. It was square in 6 series. I hope we won’t have Garmin forum posts about broken vibration motor glue and loud vibration sounds. Mine is already loud, but it’s probably due to distance between the watch strap and the pin on the casing.

Garmin Fenix 7X Solar flashlight LED board.

Another difference is we have a little board on top of the case, which holds the LED lights. It’s connected with four metal pins to the motherboard.

Garmin Fenix 7X Solar button electronics.

Also another difference is around the buttons. Previously, watch case only hold the external buttons and springs. Buttons pressed electronic buttons mounted on the motherboard. Fenix 7 series have a different arrangement. Electronic button is fixed to the case, and it’s connected to motherboard via metal pins. Motherboard only has medal pads on the corner, so that pins can touch it. There may be a few reason why Garmin chose this method. Replacing the motherboard is cheaper now, ‘cos they’ll replace less parts. This way faulty buttons are easier to replace. Just remove the faulty one and put in the new one, and they can use the same motherboard, still. Also servicing the motherboard is easier as you don’t accidentally break some buttons on the motherboard. I didn’t try to remove any button from the case, however, I liked this design as once, I saw a Fenix with one internal button broken and thus, not functioning.

Garmin Fenix 7X Solar WIFI/BLE antenna.

On the bottom side, there is a tiny wire which should be Bluetooth, BLE and WiFi antenna.

Garmin Fenix 7X Solar USB cable pins
Garmin Fenix 7X Solar optical sensor and vibration motor ribbon.

Optical heart rate sensor is below the battery and I didn’t want to remove the battery as it’s fixed well in it’s place.

Motherboards are good pieces of art nowadays. However, just be careful not to break or flex long spring pins on it. Otherwise, you may have GPS issues or other issues.

Garmin Fenix 7X Solar front side of the motherboard.

There is a big metal EMF shield on one side of the motherboard. There is a buzzer under that shield. On the otherside, there is simply a black tape so that not any metal contacts or parts touch it.

Garmin Fenix 7X Solar backside of the motherboard.
Garmin Fenix 7X Solar motherboard, under the shield.

Removing the shield is a bit hard as it’s mounted from lots of points in different locations. But under that hood, we have all the goodies we need to run, hike, ride, walk etc… Now let’s look under the hood.


MRT595SFFOC is the brain of the device. It’s NXP’s low power crossover processor MX RT500. I.MX branding reminds me of heritage of Freescale Semiconductor which NXP acquired a few years ago. Previous Garmin watches used Freescale CPU’s too.

İ.MX RT500 block diagram.

It contains an ARM Cortex M33 CPU and also Cadence Xtensa Fusion F1 Audio Digital Signal Processor (DSP) CPU. ARM Cortex M33 is an update over older ARM Cortex M4 technology and Cadence Xtensa Fusion F1 DSP is probably responsible for audio processing and maybe other dijital signal processing needs. Both processors has hardware floating point units. Both can run at up to 200 MHz frequency. However, as usually purpose is power saving in these devices, they may be running at much lower frequencies. Another new thing for Garmin is this processor has a GPU. It’s for 2D vector graphics and can run at 200 MHz speed. Garmin Venu and Epix has AMOLED screens with higher resolution displays with support for much more colours. This creates a need for more memory and processing power. Additionally, new generation Garmin watches have touch screen and you wouldn’t want the object on the display move a second later you move your finger. Thus GPU and better LCD controller is needed on newer watches. Also this processor has 5 MB of on chip SRAM. Yeah, it has 5 MB RAM on it. Actually, this is not a single large 5 MB block, but there are 32 different blocks with size ranging from 32 KB to 256 KB. Each block can be powered of independantly so that unused RAM may be powered off or put to low power mode to save power. Also subsystems such as graphics and DSP can access the memory via 64 bit interface while Cortex M33 access at 32 bit interface. There are lots of other things about this chip, however, it’ll take too long to finish.


THGBMJG7C1IBAIL is a 16 GB eMMC 5.1 2D 15 nm, SLC flash memory from Toshiba. Other Fenix 7 models like saphire models have a different chip here with 32 GB support. It has memory management features like error correction, wear leveling etc. I wish this one had 32 GB chip too, as 16 GB may not be enough for storing multiple maps and lots of music onboard. However, I simply prefer downloading and using country maps from sources using OpenStreetMap data.

Maxim MAXMAX20360.

MAX20360. Here comes the power management IC of the device from Maxim / Analog Devices. It does all the battery management and power management duties on the device, simply acts like a power substation inside the watch.

Silicon Labs RS9116-B00.

RS9116-B00 is supplied from Silicon Labs and responsible for connections to the outer world like WiFi and Bluetooth.

Silicon Labs RS9116 B00 block diagram.

WiFi works at 2.4 GHz and supports a bandwidth up to 20 MHz with IEEE 802.11 b/g/n single stream. It has Bluetooth capabilities with dual mode Bluetooth 5 support. It supports Bluetooth 2.1 + EDR, Bluetooth Low Energy 4.0 / 4.1 / 4.2 / 5.0. Blueooth and WiFi signals are emitted from a tiny wire glued to casing. The chip supports concurrent WiFi and Bluetooth but our devices won’t let this. Also this chip may be responsible for the ANT+ connection too but I couldn’t see anything about it in the documents.

Airoha AG3335MN.

AIROHA ARM AG3335MN is the GPS (We should prefer to say GNSS nowadays.) chip of the device. It is a continuation of older MTK chipsets and used by many other brands in their watches. Previously Garmin used MTK 3333AV in older Fenix’es like Fenix 2, Fenix 3, Fenix 5 etc. and they all had their own (in)accuracy posts in Garmin forums. Later Garmin switched to Sony chipset with a perfect low battery usage, but GPS posts continued. So actually I was fearing from returning to MTK/Airoha chipset. However, it seems it does its job well. All my GPS tracks seem to be well without jumping me from roof to roof and battery consumption is good as well.

Now this chip has two versions, AG3335M and AG3335MN. Airoha website has a note saying AG3335MN only support IRNSS in L5-band. So it means they both support almost same bands, but MN version supports IRNSS only in L5-band. Maybe they wanted to write AG3335MN supports L5-band only in IRNSS. Thus previously I thought AG3335MN supports L5 bands. Also some other sources said it does, depending on the SDK info. So I thought Garmin may be using this chipset in both dual band and single band GNSS watches and just using a hardware or software switch to disable L5 frequency in single band watches. This still may be the case, but also it may not be. I haven’t seen the SDK myself. There is no other device using AG3335MN with declared dual band support. Usually they’re single band boards or boards made for Indian market. Also even such manufacturers use these chips in Indian products differently. One uses AG3335M with L5 support in IRNSS and other GNSS. One uses AG3335MN with only L5 support in IRNSS. So still I’d like to see inside some dual band Garmin watches like Garmin Fenix 7 Sapphire models but I think even if they use the same SDK and almost the same firmware AG3335MN doesn support dual band except IRNSS. Also power consumption figures seem same, so they may be same inside but with features disabled.

Personally, I’m not sad about Fenix 7X Solar doesn’t support L5 bands, my tracks are already good enough for me. However, nowadays autolap started to alert me earlier in my run track. So Garmin may have break sth. with their software updates again. 😀 Anyway Garmin didn’t prefer the old chipsets with long inaccuracy posts and prefers to use a newer chipset. It has support for orbit prediction where watch downloads the GPS almanac so that it accelerates first fix.
This is not only a GNSS chip but System In Package chip with application processor, communication interfaces and other modules. It has ARM Cortex M4 CPU with FPU and MPU support. It can run at 530 MHz but we know Garmin uses it in much lower setting to save power. Multiband feature may be using a higher frequency setting as it uses much more battery. It can run at  26, 192, 384, and 530MHz frequencies. It has 664 KB RAM, 80 KB retention RAM and 32 KB L1 cache. It has some communication features like USB support, SDIO, UART, SPI support etc…

Ambiq Micro Apollo 3.

AMAP3. It is Apollo3 series chip from Ambiq Micro. I don’t know the exact reason for placing it inside but, I think it functions like a sensor hub. Sensor hubs are low power and runs at low frequencies and process data from various sensors while the main CPU is sleeping. When the main CPU awakes hub sends the data to main CPU and it processes it to display us in a beautiful format. Apollo3 seems to have a Cortex M4F CPU core that can run up to 48 MHz and even 96 MHz in power sucking turbo mode. It has 384 KB of SRAM memory and 1 MB flash memory as a storage. Blue series even have Bluetooth 5 support but I think this chip is simply Apollo 3 or I don’t exactly know which is this.

100TB2n. Some chip by NXP. But I don’t know what it does.
S4-122. ST Microelecronics 3-axis accelerometer/gyroscope.

There are other small chips on the board. Regulators, sensors etc. lots of chips. However, they don’t have useful information on them. So I can just make wild predictions about them which is not right.

Here you saw the building blocks of a Garmin Fenix 7X Solar. Yeah, there are parts I can and want to dive deeper like solar charging but I want my watch in functioning state after the process. 🙂 In seven series we saw some good upgrades like a CPU with a newer architecture, a newer GNSS processor etc. Touchscreen, itself is a valuable upgrade in my side. Simply a good sports watch to have. There are some misteries as well. Fenix 5X had 32 MB RAM chip for using with maps. Fenix 6 series had 16 MB additional RAM chips. However, in Fenix 7X I couldn’t find such a chip. Maybe 5 MB SRAM on the CPU is enough, maybe it uses some amount of storage chip as RAM.txt file is still over 20 MB. I don’t know but it does the job and does it faster. 🙂

All these upgrades are appreciated until some point and that’s the price. These watches are expensive man, expensive. If you don’t need the latest model, just go with the Fenix 6 series, Forerunner series etc. Basically all do the same, recording your run, ride, walk… Maybe Vivoactive or Venu series are good enough for you. You can also find watches using the same parts for the half or quarter of the price. Software is another point which takes the experience down too. After months from release of Fenix 7 series, still using some ConnectIQ widgets breaks GPS recording of your activity. A function 6 series could easily do but 7 can’t and not sure Garmin even wants to make it work…

Now I’ll make use of this hardware and go to run with some music in my ears… 🙂

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