Faster RAM won’t help if the soldered stick is slow.

No, not really. If your laptop has soldered RAM and an open slot, the system will run all memory at the speed of the slowest module. That soldered stick becomes the bottleneck. You could install the fastest SODIMM on the market, and it’ll just get dragged down to the same speed.

Some laptops are smart enough to run the two channels at different speeds, but that’s rare and usually not worth counting on. Most just default to the lowest common denominator. So you’re stuck with whatever the soldered RAM is rated for.

If you’re trying to add more RAM for capacity, go ahead — more memory helps. But don’t buy a faster stick thinking it’ll speed things up. It won’t.

This is one of those times where soldered RAM is just a raw deal. Future you might want to check for dual-slot laptops next time.