change firmware on garmin nuvi 500

What you are trying to do is way beyond what 99% of us here wish to do. We are trying to squeeze the most out of the devices as Garmin gave them to us. Not sure how many here even posses the capability to 'jailbreak' their devices. Good luck on your quest though.

http://static.garmincdn.com/pumac//2650_OwnersManual.pdf

if you connected the GPS to a Linux box and mounted it as a drive you might be able to transfer a thumbdrive version of Linux (My favorite is Puppy)

But what functionality are you looking for? With limited I/O possibilities I'm not sure what you're going for here.

I'm going for portable computing/router management an otg cable could be attached to the usb port and wifi usb adapters and other peripherals can be attached making it an umpc my job is usually on the go on my scooter so i need a really mobile linux machine it was laying around so i figured it may work.

There are a whole raft of issues with your dream the least of which is the software powering the device. You would have to reverse engineer the hardware and write new code to drive the display and sound system not to mention being highly constrained by the amount of memory present in the device. The processor has enough trouble just keeping up with updating the display using Garmin's code so why do you even think you could load it down with additional tasks?

The Garmin OS is proprietary and they don't publish any hooks that may be available for user written software. There have been several that have reverse engineered the data files used but I've never heard of anyone replacing the OS with a home brew.

ok so if i cant do that what can i do with the gps i have gps on my phone that works just fine are there hacks that can make it worth keeping? never had a gps before.

Sell it online, you'll get a few bucks. Or if I give my address you can donate it to me.

It's good GPS, it has some good features, it has everything most users would need. It's even waterproof.

Have a look at https://buy.garmin.com/en-US/US/on-the-road/discontinued/nuv... and then compare with other models