Thread: Gpsmap 296 & 396 - basemap updating and logo modding

I suspect most if not all of the devices from that period (StreetPilots, early GPSMAPs and very first nuvi models) used the very same basic data in region 16 with only the embedded splash image being different in some models/regional releases.

It's also likely that until release of first nuvi models (3xx/6xx) with Mass Storage Mode capability and "rrgn" command in firmware to write a region's data as a BIN file onto a media card, none of the other "region-only" devices like your 296/396 (i.e., lacking MSM) could have the data in region 16/0x10 dumped due to protection against that, although it could be over-written of course.

As for re-calculating the checksum, i don't think i've ever bothered to learn how to do that because the only result of having a mismatched checksum is a "fail" report for splash in the hidden inventory. Therefore, it's of nil consequence for day-to-day device use. I would think however that the calculation needs to be done in 8-bit to obtain a 2-character checksum for the entire new dataset but maybe then reverse the result - i simply don't know, but maybe someone who does will enlighten us, or if you find out elsewhere please post here about it, just "for the sake of science" (and to satisfy my vague curiosity) - because that's getting a bit deeper into the weeds than what we usually do here. It's not really OT though ....