Author: Michael George
Created: 7 Jun 2025
Updated: 10 Nov 2026
The FIT files from Garmin watches / products often contain a product number for the GNSS chipset. The GNSS product number can be found in the device_info record with a device_type of 0 (GPS).
This document summarises the GNSS product numbers and where they have been observed in FIT files. Unfortunately, newer watches from Garmin have stopped distinguishing between the chipsets and simply user the product number of the watch (e.g. fenix 8 and newer).
A number of methods to identify the GNSS chipsets in Garmin watches can be found via this first link. An extensive list of Garmin watches and their GNSS chipsets can also be found via this second link.
Some brief notes about the GNSS chipsets in Garmin watches since 2024:
A lot of this recent history is based on photos provided by the Federal Communications Commission (FCC).
| Released | Watch | Multi-Band | Chipset | Comment |
|---|---|---|---|---|
| 2024-08 | fēnix 8 | Y | SYN4778 1 | 47762 is present in FCC photos - prototyping? |
| 2024-08 | Enduro 3 | Y | SYN4778 1 | 47762 is present in FCC photos - prototyping? |
| 2025-01 | Instinct 3 | Y | AG3335M | Airoha is clearly evident in FCC photo |
| 2025-01 | Instinct E | - | TBC 2 | Airoha is clearly evident in FCC photo of Descent G2 |
| 2025-02 | Descent G2 | - | TBC 2 | Airoha is clearly evident in FCC photo |
| 2025-04 | vívoactive 6 | - | AG3352B | AG3352 is readable in FCC photo, but B is obfuscated |
| 2025-05 | Forerunner 570 + 970 | - | SYN4778 | SYN4778 is readable in FCC photo of FR 570 |
| 2025-06 | Venu X1 | - | AG3352B | FCC photo is obfuscated, presume AG3352B like VA 6 |
| 2025-09 | fēnix 8 Pro | Y | SYN4778 3 | SYN4778 is clearly readable in FCC photo of the 51 mm |
| 2025-09 | Instinct Crossover AMOLED | Y | SYN4778 | SYN4778 is clearly readable in FCC photo |
| 2025-09 | Venu 4 | Y | SYN4778 | SYN4778 is blurry but readable in FCC photo |
| 2025-09 | Bounce 2 | - | AG3352B | AG3352B is clearly readable in FCC photo |
| 2026-05 | Forerunner 70 + 170 | - | AG3352B | AG3352B is clearly readable in FCC photo of 170 Music |
| 2026-08 | fēnix 9 + fēnix 9 Pro | Y | TBC 4 | |
| 2026-10 | Enduro 4 | Y | TBC 4 |
Notes:
Several product numbers have been observed for the MediaTek MT3333.
It’s worth noting that some watch models have been seen with differing GNSS product numbers. e.g. Forerunner 920XT with 1620 and 2957.
It is unclear whether these are slightly different versions of the MT3333, updated Garmin GPS software, or firmware updates from MediaTek.
| Product | Chipset | Observed |
|---|---|---|
| 1619 | MT3333 | Edge 520 |
| 1620 | MT3333 | fēnix 3 fēnix 3 HR Forerunner 920XT |
| 1621 | MT3333 | Forerunner 935 Forerunner 645M |
| 2957 | MT3333 | Edge 520 Plus Edge 820 Edge 1030 fēnix 5 fēnix 5 Plus fēnix 5S Plus Forerunner 920XT vívoactive 3 |
| 3411 | MT3333 | Forerunner 735XT |
| 3750 | MT3333 | fēnix 5X fēnix 5 Plus Instinct Esports |
Multiple teardowns confirm the MT3333 being used in a variety of Garmin watches from this particular era:
Several product numbers are observed for the Sony GNSS chipsets.
It’s worth noting that some watch models have been seen with differing GNSS product numbers. e.g. Forerunner 945 with 3107 and 4197.
3107 probably represents the CXD5603GF, but others may represent chipsets such as the CXD5605GF, or relate to firmware updates from Sony.
| Product | Chipset | Observed |
|---|---|---|
| 3107 | CXD5603GF | Edge 530 Enduro fēnix 6 fēnix 6 Pro Instinct Solar Forerunner 945 Swim 2 |
| 3799 | CXD56xxxx | Edge Explore 2 Instinct 2 Forerunner 745 |
| 4058 | CXD56xxxx | Forerunner 55 |
| 4197 | CXD56xxxx | Edge 530 Edge 830 Forerunner 245 Forerunner 945 fēnix 6X vívoactive 4 |
Teardowns:
Information:
There are three distinct product numbers for the Airoha GNSS chipsets; 3865 (AG3335M, multi-band), 3866 (AG3335MN, single-band), and 4548 (AG3352, single-band).
One anomaly has been spotted where the fenix 7 Sapphire lists the GNSS product number as 3866 (AG3335MN), despite being multi-band. This is likely because there is a single product number of 3906 for the fenix 7 series, so the system software may not distinguish between the various models.
The Instinct 3 and Instinct E refer to the AG3335M and AG3335MN respectively. They also exhibit the same artefacts in gps_metadata as other Airoha-based Garmin watches. These observations are software-related, but strongly suggest the Instinct 3 and Instinct E are using Airoha chipsets.
| Product | Chipset | Observed |
|---|---|---|
| 3865 | AG3335M | Edge 840 Edge 1050 epix Pro (Gen 2) fēnix 7 Pro Forerunner 255 Forerunner 265 Forerunner 955 Forerunner 965 Instinct 2X Instinct 3 |
| 3866 | AG3335MN | epix (Gen 2) fēnix 7 fēnix E Forerunner 165 Instinct E Descent G2 Venu Sq 2 Venu 3S vívoactive 5 |
| 4548 | AG3352 | Bounce 2 Forerunner 170 vívoactive 6 |
Several teardowns show the AG3335M:
Several teardowns show the AG3335MN:
Several teardowns show the AG3352B:
Early system software for the fēnix 8 recorded the GNSS product number as 0.
e.g. system software = 12.35, GPS software = 2.11, GNSS product = 0.
Subsequent software has recorded a GNSS product number which is identical to the fēnix 8 product number.
e.g. system software = 13.37, GPS software = 2.17, GNSS product = 4536.
Likewise the Forerunner 970 also records its product number (4565) as the GNSS product number.
| Product | Chipset | Observed |
|---|---|---|
| 4536 | SYN4778 | fēnix 8 |
| 4565 | SYN4778 | Forerunner 970 |
| 4678 | SYN4778 | Instinct Crossover AMOLED |
Several teardowns show the SYN4778:
Several FCC teardowns show the SYN47762:
GNSS product numbers have been quite useful when trying to distinguish between MediaTek, Sony and Airoha chipsets.
Sadly this may be coming to an end with the fēnix 8 and Forerunner 970, which do not use generic GNSS product numbers.
Future insights are likely to be reliant on photos provided by the Federal Communications Commission (FCC).