Best,
Is IQ Routes really
effective on a TomTom one 1st (with a navcore 9)?

It depends on whether the navcore has a swap file but even then it can be problematic

My naccore 9.450 has, in fact, a file named "swap" and with the 11959 maps a message is displayed : "fastest route, IQ routes" with also today's date...
How does the One 1st recover this latest information? if he gets them...

[Please Register or Login to download file] IQ routes Englisch
As you can read at the end of this article with every new map the IQ routes are updated. So use a new map after 3 months
Tick the box for the IQ route and look wat is the calculation time for the route and how long is the distance.
Then do the same without IQ route and look wat is the calculation time for the route and how long is the distance.
Most of the time there is not much difference between the distance only between the calculation time.
As Fredderf said it can be problematic so don't use the IQ route option (don't tick that box)
(It consumes too much memory for the old One)
Personal I think most of the time IQ route is not effective on a TomTom and not only the one (also 720/730 etc)
Instead tick in the planning preferences the box:
If the traffic situation changes and we discover a significanly faster:

1. Always switch to that route
2. Ask me if I want that route

Thank you for your answer... I did the test on 500 km routes. Indeed, there is less than 5 minutes difference (with and without route IQ) and the One calculates much faster without route IQ.
Regarding "traffic" monitoring, it works well on my "740 live" although it is not always relevant... but it is not functional on my "One 1st".

For Bency:
Check that the card is compatible with the navcore installed (see "status and information" on the TomTom). Simply copy the map folder to the root of the TomTom, also add the "FastActivate" app and run the first three patches, that should do it...
Otherwise, follow the tutorials on the site (very well explained) to change navecore...