> I hadn't even imagined this constituting "brute force". Is my phone using "brute force" to find the WiFi router?Early receivers were a lot less advanced than modern receivers - one of the key functions of the almanac is to help receivers figure out what satellites they can expect to see - thus greatly reducing the range of gold codes and time offsets they have to check.
Unlike wifi, GPS signals are below the noise floor until the gold code is applied to despread the signal, and the gold code has to be synchronized with the received signal to detect it.
The gold codes are pseudorandom and designed to stop signals interfering with one another. Unless you know which gold code you're looking for, and find its time offset (accurate to about 2 chips in 1023) you can't tell it apart from noise.
You also don't quite know the frequency you're looking for - partly due to the imprecision of the receiver clock, partly because GPS satellites move very fast and so can have a lot of Doppler shift (depending on where they are in the sky relative to the receiver of course)
Back when receivers had more limited physical hardware, searching through ~30 different satellites, multiplied by ~500 different gold code offsets, multiplied by a few different Doppler shifts could be a slow process. Especially if you'd found a handful of satellites, so some of your receiver channels were tied up with tracking leaving you with fewer for searching!
So ignoring the almanac and brute forcing every satellite, gold code offset and doppler shift is one of the many ways performance has increased since this stuff was developed in the late 1970s.