Currently I have a 64MB SanDisk MicroSD card in the slot in the battery compartment. When I upload tracks, waypoints, and maps into the unit, the upload seems to truncate (with no warning message) track data .... I'm hoping that upgrading memory might let me save all tracks.
What's the largest MicroSD chip I can use on Garmin eTrex Vista Cx?
When the products were launched in Jan 2006, 512MB was the largest available on the market, so the manuals and Garmin's web site answered this question with "512MB". You can still find references with that outdated answer.
1GB and 2GB MicroSD cards becamse available later in 2006. They work fine. Garmin specifially warns against the SanDisk Ultra II 1 Gb.
In 2007, 4GB and 6GB microSDHC cards became available. However, the units remain bound by a 2GB limit for a single map file in most mapping products. That's not terrible; 2GB holds the entire U.S. for any Mapsource product. The GPSes are limited to 2025 map tiles and the Topo product, in particular, uses tiny (county sized) tiles so it's easy to run into that limit long before you run into the 2GB limit.
City Navigator Europe v9 (NT-not) has been confirmed to support maps > 2GB and it appears that the 2GB limit still holds true if multiple mapping products are used.
http://www.gpsfaqs.org/faqs/garmin/xser ... estmicrosd