How do laptops manage to deliver very decent performance despite drawing just a fraction of how many watts a desktop draws?

Question

Take a laptop with a mobile graphics card. Mobile graphics cards obviously perform worse than their desktop counterparts. I would say they perform like the next lower tier on desktop (e.g. an RTX 3080 Mobile performs about as good as an RTX ~~3070~~ 3060TI desktop card according to UserBenchmark (yeah, I know, not the best site, but close enough in this case). But the mobile card still only less wats.

Example: [https://www.youtube.com/watch?v=Hz9GfxCAXgs](https://www.youtube.com/watch?v=Hz9GfxCAXgs)

This laptop uses a 200 watt charger. How can a 200 watt charger power a 3070 and an i9 processor? Even if they are just the mobile variant, isn’t that almost like expecting a 200 watt power supply to run a 3060 TI and an i7 processor from the same generation? Heck, we don’t even run 75 watt cards like GTX 1650s and 60w CPUs like some i5s and i3s on 200 watt on desktops. So what gives?

In: 27

Answer 1

Couple of things, laptop parts tend to have a few extra optimizations for power. They are also custom designed for their specific needs. This adds up, and they don’t put in an oversized PSU. Specifically, when you hear people recommending a 750W PSU for a gaming system, it’s because they need specific current ratings on specific power rails, and it’s easier to spec a PSU that is guaranteed to have that than add them up for each rail. On a laptop they do add them up.

So the toms hardware review said their test with a 3080 rig used only 334W, and best I can find a GPU-only test of a desktop 3060 Ti used only 193W peak, that desktop system with everything in it probably uses 250-300W total. Most people are way over specing their home desktop PSUs, if you actually did the math and added up actual numbers most people’s gaming systems will run with a 450W PSU.

Laptop parts typically do have some different manufacturing stuff done to lower consumption, for example they typically run the parts at 20-30 degrees C higher, because it makes the heat sink more efficient and means less power spent on the fan. Also, a not insignificant amount of power is used by the memory, so reducing or slowing down memory can get a big power savings, even though “it’s the same GPU”.