how many maps?

after trying various search options, I thought I found an answer in the forum. However, it talks to the 7x0 nuvi and says just one map on the sd card.

does that apply to the 650 as well?

You can put a different map on however many SD cards you want and then just put in the card you want to use. Not much trouble to change out cards and they are cheap too.

so I take it you can't have 2 maps on the same card?

I like to know if it's possible too

No, you can't. Not sure why you'd want to do what's outlined in the OP.

However, you CAN have three different mapsets loaded.

The unit will read the GMAPPROM.IMG (the preloaded maps), and a different GMAPSUPP.IMG file on both the unit and the SD card, at the same time.

But you probably don't have room on the unit itself to load a supplemental map of too big of a size.

Thanks for the info )

thanks for the help

You can have many more than 3 maps, on any unit. Don't confuse maps with files. A file can contain more than 1 map. A map is what's selected for display.

For instance, the standard file included with US units, covering US and Canada (City Navigator North America NT), has 1 map with 63 map regions in it, one for each state and province.

Garmin's Mapsource program allows maps/regions to be assembled into files (which Garmin calls a "map set").

The following is accurate for a nuvi 660, it may be different for other models, but the concepts are similar.

On Nüvi you can have these files on the internal flash:
gmapprom.img (normally preinstalled maps)
gmapprom1.img (used when both EU and US are on the GPS)
gmapsupp.img (maps downloaded to the GPS)
gmapbmap.img (base map, can't be "unselected")
gmapoem.img (Oem maps?)

There is a 2 GiB limit to the size of these files.

On an SD card you can only have gmapsupp.img. I consider this a hugely stupid design flaw of Garmin's, since an SD card can easily be larger than the provided internal flash.

The map _region_ limit of a nuvi 660 is 4005. That's may be the map limit as well, but there aren't nearly that many maps available. If your internal map is City Navigator North America NT, that takes 63 regions, so your other map sets must have less than 4005-63=3942 regions.