1. Introduction : Until 2005, Garmin GPS systems, be they handheld (eTrex, G60/G76), mixed (GPSV), car (SP2610, C320) or Marine (GPS276) used a "low sensitivity" Garmin chipset, with little correlation power. This meant long acquisition times (you could help by giving an approximate position), frequent loss of position in difficult environments (dense urban areas, forests with thick tree cover, etc...) and no operation at all (coated windshields). On the other hand the position was very stable as the module could only work with "clean" signal.
2. The Move to High-Sensitivity : SiRFstarIII : This all changed in mid-2005 when Garmin announced they would be using the high sensitivity SiRFstarIII chipset in their upcoming nüvi car system and a bit later in the 60/76 Cx handhelds. The SiRFstarIII chipset was launched by SiRF in early 2005 to take over from the SiRFstarII chipset that was already more powerful than the old Garmin chipset, respective tracking ratings being -159dBm, -148dBm and -143dBm (the lower the better). Acquisition sensitivity remained at about -143dBm as this is the level of signal required to download the live ephemeris data from the satellites needed to calculate a position, but with its massive correlation the power, the SiRFstarIII was able to scan the sky for satellites and TTFF (time to first fix) was much faster, provided that minimum level of signal was available.
This move was applauded by most users as it made acquisition times in the morning much more consistent, never more than a minute in good conditions, a bit more while driving and the GPS systems kept tracking virtually everywhere, including indoors, not that it was really useful...The flip-side was that very weak satellite signals were now being used, resulting in a much less stable position, one of the reasons to stick to low-sensitivity systems for marine GPS systems.
3. High-Sensitivity Galore - MTK, STMicro Teseo, STMicro Cartesio
Starting in the summer of 2007, Garmin diversified their supply of high-sensitivity GPS chipsets, using the MTK v1 (Mediatek) on the eTrex Hcx range, the ST Micro Teseo integrated platform (codename "bravo" ?) on some nüvi 200 models and the ST Micro Cartesio on the nüvi 2x5 in early 2008. In October 2008, some eTrex H receivers appeared with a new "mystery" chipset, "bravo 3", since previous eTrex H models used the MTK v1 (3318) chipset, it could be the MTK v2 (3329) chipset used on the Qstarz Nano Bluetooth GPS Datalogger.
Garmin no longer communicate on the chipset they use (SiRFstarIII was disclosed as being the chipset of the nüvi was launched in late 2005) and naturally haven't commented on the switch to other suppliers, but it's likely a mix of diversifying their sources, segmenting their offering (SiRFstarIII remains the "top choice") and getting better pricing (fully integrated ST Micro platforms for instance).
While the GPS performance of all current systems is excellent compared to what was available only 5 years ago, especially with the addition of Auto-AGPS/HotFix (ephemeris data is generated on-board to reduce the TTFF) in 2008, but it's always interesting to know what's "inside" our GPS systems and some variations remain (SiRFstarIII still offers the most "dynamic" position at slow speeds), so here is a list of Garmin systems grouped by the type of GPS chipset being used. In some cases Garmin switch the chipset on a same model, the FW version is a clue to see which one it is.
4. GPS Chipsets and GPS Systems - Sorted (in order of appearance)
1. SiRFstarIII (type G) : Latest firmware version : FW v3.00s - 12/2007
1. Sports systems : Edge x05 (AGPS on 605/705), Forerunner 205, 305 and 405 (AGPS ?)
2. Handheld systems : 60Cx, 60Csx, 76 Cx, 76 Csx
3. SP 5x0 : discontinued
4. nüvi 2x0 : some early models
5. nüvi 3x0 : all models, now discontinued
6. nüvi 6x0 : all models, now discontinued
7. nüvi 7x0 : early models, switch to MTK in the summer of 2007
8. nüvi 5000 : unconfirmed
2. MTK v1 - MTK3318 (type M/M2): Latest firmware version : FW v2.80m - 10/2008
1. Handheld : eTrex Hcx series (Vista, Legend, etc...), Colorado
2. nüvi 2x0 : some nüvi 200/250 models
3. nüvi 260 : all models (?)
4. nüvi 7x0 : some (all?) models starting summer of 2008, see details
5. nüvi 7x5 : all models
6. nüvi 8x0 : all models
3. MTK v2 - MTK3329 ? (type ?): In October 2008, some eTrex H receivers appeared with a new "mystery" chipset, "bravo 3", since previous eTrex H models used the MTK v1 (3318) chipset, it could be the MTK v2 (3329) chipset used on the Qstarz Nano Bluetooth GPS Datalogger.
4. ST Micro Teseo (type B ?): Latest firmware version : FW v3.10b - 01/2009
1. nüvi 2x0 : some nüvi 200/250/260 models, codename "bravo"
2. nüvi 5000 : all models ? Details here
5. ST Micro Cartesio : Latest firmware version : FW v2.55b - 10/2008
1. Handheld : Oregon 200/300/400 with HotFix
2. nüvi 2x5 : all models
3. nüvi 5x0 Crossover : all models
NB: Garmin Rino 530HCx е тип B.