Here is something interesting I found

http://www.gpsinformation.org/dale/nmea.htm#sirf

Look at NMEA sentence $PSRF104.

It appears there is a way to shorten the initial lock time by providing the SiRF chip with

- current location and altitude
- current time
- initialization mode:

1 = warm start, ephemeris valid
2 = clear ephemeris, warm start (First Fix)
3 = initialize with data, clear ephemeris
4 = cold start, clear all data
8 = cold start, set factory defaults

I am guessing it is gpsdriver who issues these sentences to the chip. Improving GPS performance may be as easy for Nokia as setting the right values in this sentence.

BTW, I noticed that the internal clock in my N810 is fairly inaccurate -- it loses 3-5 seconds per day. I wonder if this is a factor in GPS performance. Warm start requires accurate time, though I am not sure how accurate.