Your problem is that 2GB SD cards are measured in decimal i.e. 2GB=2,000,000,000 bytes [in theory], whereas the FAT16 file size limit [and consequently Garmin's maximum image size for older devices such as nuvi 3x0/6x0] is 2GiB less 1 byte [GiB being gibibyte, or an original binary GB] which is 2,147,483,647 bytes. Therefore a so-called 'just under 2GB' image file won't fit on a so-called '2GB' SD card which at best probably only has about 1.86GiB of usable space [~1,998,500,000 bytes]. The rule of thumb is that if the unit's internal memory is FAT16 then it cannot see an image 2GiB or over even if capable of reading FAT32 SD cards, such as 3x0/6x0 nuvi series are for instance. Those old units cannot use this unicode map effectively though of course, the EU non-unicode is the map for them.
Originally Posted by japseye
Most image files posted with the claim that they are 'under 2GB' are in fact usually just under 2GiB and therefore need to go on a 4'GB' card. Microsoft still uses the original binary meaning of KB/MB/GB/TB etc which is that 1KB is 1,024 bytes [2 to the power of 10]; 1MB is 1KB x 1024 = 1,048,576 bytes [2 to the power of 20]; 1GB is 1MB x 1024 = 1,073,741,824 bytes [2 to the power of 30]; 1TB is 1GB x 1024 = 1,099,511,627,776 bytes [2 to the power of 40]. So in Properties it will report quite correctly [in binary] that your 1GB card has only ~938MB or ~0.916GB, a 2GB has ~1.84GB, a 4GB card has ~3.72GB, and an 8GB has ~7.39GB in usable space only.
It's also possible to format a 4GB [~3.72GiB] card in FAT16 so that very old units such as StreetPilots which can't see FAT32 can read them and use an image up to 2GiB [2,147,483,647 bytes] instead of being limited on a 2GB card to an image of ~1.86GiB [~1,998,500,000 bytes]
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