The better question is if you are running out of GPU memory now, with what you presently have.

If you are not running out of GPU memory, or render in Firefly, having more memory gpu memory wont help anything.

So unless Superfly is presently erroring out from not enough GPU memory with what you do, you don't need 12 or even 16gig of gpu memory.

The speed difference between a mobile 4080 and a mobile 4090 is only about 11%, and you will use more than 11% more power to get that with the 4090 mobile....

Don't expect the battery to last long in a notebook doing that.

Keep in mind that a mobile 4090 is a nerfed desktop AD103 chip... A massively nerfed 4080 desktop chip at that.

Honestly, I would not want to be using the gpu in a notebook for compute. Or an I9 with Firefly in a notebook. That is a lot of heat, in a small place....

I use a 4070ti with 12 gig to render in my desktop, and I rarely run out of memory. A 4070ti is also faster than a 4090 mobile will ever be...

So the choice comes down to what render engine you use, how much memory you actually need for what you do, and how happy you will be when that notebook burns itself up and no one can repair it because everything in it is serial locked in the bios.... ( A fun tidbit about Lenovo system, that most people don't know.... )

Notebooks are no where near as fast as desktops either. And if you do use Superfly, you don't even need an I9. My system has a 13600k I5, and 20 cores is more than enough for Poser when using Superfly, Studio with Iray, etc.

You could buy a 13th or 14th gen desktop for the same money, that will run circles around that notebook.

It will last longer as well.

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