Max cardsize for uSD 32/64/128 ?

Discussion related to the Garmin GPSMAP 66 series GPSr
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Max cardsize for uSD 32/64/128 ?

Post by g66 » Tue Jul 23, 2019 4:07 pm

Garmin says 32 GB with Fat32
64 GB should also work fine -->
Did someone test 128GB ?

For example - backup of internal on uSD in some generations would be possible :-)

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Re: Max cardsize for uSD 32/64/128 ?

Post by Themistokles » Tue Jul 23, 2019 7:09 pm

Please don't take me as an expert in this field. However, I somewhere have read that it is more a matter of the sort of the card than of the size of the card. That is, Garmin was said to have designed that device (like many others) to work with SDHC cards, not with SDXC cards. That in turn probably means that we should stick with 32 GB, because that is the maximum size of SDHC cards (as far as I know).

As I have said above, I am no expert. But this is what I remember.

On the other hand, I also have read that people have used SDXC cards in that device. I am sure that you won't damage anything when you just try it, but see the next section ...

Personally, I'll stick with SDHC and 32 GB. If trying something else / larger, you should at least test what happens if you actually let the device put 120 GB or 60 GB (in other words, a little bit less than the maximum capacity) onto the card. With other devices, I have seen all sorts of failure in similar situations. For example, a size of 64 GB was reported to the O/S, but the O/S or firmware could only handle 32 GB and "wrapped around" once 32 GB were full, effectively overwriting existing data (think of it like a ring buffer).

I wouldn't trust the statements in a post where some guy claims that "it works", unless that guy is a recommended expert. Otherwise, at least ask him if he did thorough tests, including trying to write the card to its maximum capacity in the device itself (i.e. not in a card reader at the PC). If a device just recognizes a card (even with the correct size), that doesn't mean anything in the first place ...

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Re: Max cardsize for uSD 32/64/128 ?

Post by sussamb » Wed Jul 24, 2019 4:54 am ... ImFS8HFIxA

However larger cards will work but they must be formatted FAT32, larger cards are not FAT32 by default.

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Re: Max cardsize for uSD 32/64/128 ?

Post by Spiney » Wed Jul 31, 2019 5:20 pm

Here is a (lengthy) post from the Garmin forum demonstrating that a 128Gb card works in a GPSmap 64 ... 418#772418, so it should work in a 66 too.

The author loaded a 128Gb card with City Navigator, the Topo US 24k maps, Birdseye Topos, Birdseye hi-res satellite images and some GIS maps and GPX files of mine locations for the whole of Arizona ... so it can be done.

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Re: Max cardsize for uSD 32/64/128 ?

Post by Art » Tue Aug 13, 2019 2:28 am

There’s no difference between SDHC cards and SDXC cards other than the file system they come formatted with.
Larger cards work fine when they are formatted as FAT32.

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