[Upgrading, Modifying and Unlocking] yellowfever:
You are very welcome, and I am happy that I can finally give something back to the community ;)

- Sorry, I know no way how to dump the original firmware.

- 2.5.0 definitely works great here... don't know why not for you. Please try with SirfDemoPPC to see what's actually happening.

Well, this is what I was working on the last days. By now I am pretty sure that everyone claiming to have gotten this stuff to work so far probably just saw a placebo effect. Either that, or I am totally dumb :P

The problem seems to be that the "GPS Intermediate Driver" from the N5xx does NOT work on the T830. Here's a simple description of what I understand should be going on if quickgps / sirfinstantfix really works OK:

- Set the date, time, and location correctly in the system

- Use any way (for example QuickGPS software, or manual download) to download the file packedEphemeris.ee to the \windows folder

- To use this feature all GPS software MUST connect to the SOFTWARE (virtual) port (Microsoft GPS Intermediate Driver), not the GPS-Chip at COM6 directly!

- When the software COM port is opened by the GPS software, the driver (probably gpsid.dll) unpacks the packedEphemeris.ee file to a new file called ephdata.clm

- The GPS firmware finds a first sattelite, and gets the GPS time

- Then the GPS firmware will, for every satellite it sees, give an message like "what is the ephemeris (location data) of this satellite?" to the serial bus

- The GPS intermediate driver sees this message, calculates the ephemeris data from the ephdata.clm, and sends this to the GPS firmware over teh serial bus

- The GPS firmware can now also use more satellites for a fix than before (because it has the calculated ephemeris even if the signal is too low to download the ephemeris from the satellite)

- And of course at startup it doesn't need to wait for 3 (or 4?) satellites' ephemeris to be completely downloaded, this is why TTFF (time to first fix) is faster with this feature

Note: Newer GPS firmwares already help a bit getting faster fix, because according to the release notes they don't need a satellite to have a strong enough signal for the complete time it takes to download it's ephemeris, but it can partially download the ephemeris and then only needs the rest of it the next time the satellite sends it

So far it seems noone has ever seen the "ephdata.clm" on the T830, and thus we can be reasonably sure that they did not really use the sirfinstantfix feature. Also it can not work with COM6, so people using COM6 can't be getting this working either...

I have kinda given up, and resorted to the following "workaround"... you may call it "Manually assisted SirfInstantFix" ;)

- Only use COM6 directly (SirfDemoPPC doesn't seem to work with the intermediate / virtual driver)

- Manually download packedEphemeris.ee

- Start SirfDemoPPC

- set the chip to Sirf mode

- Load the .ee file

- do a warm start of the GPS

- when the display turns blue again (=sees at least one sattelite) do a hot start of the GPS

- wait until the fix is there (usually < 10 seconds), and some more time until some more satellites show up as purple (using calculated ephemeris) or green (using downloaded ephemeris)

- switch back to NMEA mode

- Exit SirfDemoPPC

- start the GPS software

Yes, it's not automated at all :(, but for me still gives easier/faster fix, especiall when you are moving.