G'day again jinxxxxxx,

I don't have access to a GW Navi unit to test at present, but from memory there is no problem with the unit reading large cards formatted in FAT32. My SP 2610 [closely related hardware to your GW 2006 navi but with older firmware than GW navi] will happily read a FAT32 formatted 32GB CF card. As to the age-old chestnut of the file size that can be used by Garmin units of any variety, that simply depends on the FAT type they are able to read. If they can only read cards with FAT16, then they are definitely limited to a map image size of 2GiB minus 1 byte [2,048 MiB minus 1 byte, or precisely 2,147,483,647 bytes]. Many older units such as ours are also subject to that FAT16 limitation, even though they can read FAT32 formatted cards. My 32GB & 2GB CF cards have maximum capacities of 32,003,457,024 & 2,047,541,248 bytes respectively. However, microSD & SD contain even less than that. Because they are claimed to be measured by their maker in the decimal version of a 'Gigabyte' [i.e. a factor of 1000 or 1,000,000,000 bytes] my Sandisc 32 & 2GB microSD cards' capacities are 31,902,400,512 & 1,977286,656 bytes. But the principal of 'near enough is good enough' rules, and my 4GB Sandisk SD contains 4,066,902,016 bytes, like the CF cards just over their claimed decimal theoretical limit of 1GB=1,000,000,000 bytes [for 4GB that's of course 4,000,000,000 bytes]:

[Only registered and activated users can see links. ] [click to enlarge]

Unfortunately Microsoft Windows clings to the original binary understanding of a GB being binary [i.e. a factor of 1024 or 1,073,741,824 bytes]. That's not a criticism of M$, they are technically correct in the traditional sense. Microsoft's 'binary Gigabyte' is now technically known as a 'Gibibyte' in an attempt to distinguish it from the drive manufacture's hijacked 'decimal Gigabyte' but M$ is having none of that so the confusion continues as to what really is a TB/GB/MB/KB. Partly this can be solved by everyone using NIST's 'new' terms of TiB/GiB/MiB/KiB [Tebibyte/Gibibyte/Mebibyte/Kibibyte] for binary and the 'old' binary terms of TB/GB/MB/KB [Terabyte/Gigabyte/Megabyte/Kilobyte] should now be used only for decimal. Until M$ folds on that, and computer memory is measured in decimal rather than the binary interpretation of a 'GB' confusion will continue. The alternate terms were adopted by NIST 16 years ago but hardly anyone uses them in accordance with their interpretation:
Code:
Please Login or Register to see the links
Back to the image and card size relationship. Once we have our head around the above information, it's now clear that a maximum sized image file for FAT32 cannot fit on any [so called] 4GB card. This is because the image can be 4,294,967,295 bytes [4GiB or 4,096MiB minus 1 byte respectively] but that sized map image cannot fit on any SD 4GB card which has a maximum [theoretical] size of 4,000,000,000 bytes. However, if the unit is only capable of seeing file sizes up to the FAT16 limit [2GiB or 2048MiB minus 1 byte] as are your GW navi unit and my SP2610 then we are limited to that size map regardless. Similarly to the above 4MB card example for FAT32, a FAT16 maximum sized image of 2GiB/2048MiB minus 1 byte [2,147,483,647 bytes] cannot possibly fit on any 2GB card either. It must therefore go on a 4GB card.

[Only registered and activated users can see links. ] [click to enlarge]

And you're totally correct that this is a firmware limitation. The rule of thumb used to be that if the unit's internal memory was formatted in FAT16 then it could only read images up to the FAT16 maximum, even if they were on a media card formatted in FAT32. That's still the case for your GW and my related 2610, and other Garmin units such as nuvi 300/600 series and StreetPilot 300/500 series but Garmin in it's wisdom some time ago decided to allow some nuvi series [eg 200/700] to read images up to the FAT32 limit on media cards. Maybe they'll do the same for GW with future fw updates, but i don't hold out any hope at all for my SP2610 or other earlier units.