Quote Originally Posted by gkarlsen View Post
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Question 2: Does anyone know how big of an micro SD card that is supported in an Garmin Alpha 100 and an Garmin 320?
From the context seeing you mention Alpha 100 I guess 'Garmin 320' is a Garmin Astro 320. Both those devices should support a microSDHC 32GB card no problem and prob even larger SDXC cards reformatted from exFAT to FAT32, however Garmin is likely to say very much smaller than that officially. The reason is that outdoor devices have a maximum mapping segment (tile) limit as well as a limit of maps themselves so it is theoretically then quite easy to breach those limits with very large cards loaded up with mapping. For most users a card of 4GB is enough, 8GB is definitely adequate and 16GB is probably overkill. Your Alpha has a tile limit of ~3,500 and the Astro is ~3,000.

Here are a couple of threads to explain in more detail:
[Only registered and activated users can see links. ]
[Only registered and activated users can see links. ] (Post no. 18 there has specific info for your devices).