hey I was thinking of designing a small case ( based on lian li PC-OX line) so I wanted to know what is the smallest PSU for NVLink RTX 2090ti
A assume you mean by NVLINK 2080Ti, you mean looking at running a pair?
What other components do you envisage to use? a 9700k has a much different power profile vs a threadripper of X299 CPU etc.
You can see her for example a rig with a 8700k @ 5Ghz and pair of 2080Ti's in NVLINK can sit at around 750 watts or so, with some higher peeks: https://www.tweaktown.com/articles/8741/geforce-rtx-2080-ti-nvlink-4k-120fps-gaming-now-here/index10.html
You CPU will change the equation more depending on what it is also, but either way, as you would expect, will need to be fairly beefy.
so i can use https://pcpartpicker.com/product/jbZ2FT/silverstone-sfx-800w-80-titanium-certified-fully-modular-sfx-power-supply-sst-sx800-lti to power a PC that has 2 rtx 2080 ti ( I will not overclock them )
I would not.
You also neglected to mention your CPU, 8700k while it does use power, there are ones on the market that can consume more now.
Personally if with a modest OC on a 8700k and pair of 2080TIs out the box peak at near 800 watts, would defo not pick a 800w PSU, more so as I say if you get a CPU which does consume more power, you want more headroom and to sit at a more efficient point then near maxed out continuously or above depending on CPU choice.
Just my two cents, either go single 2080Ti or scale up your PSU more adequately.
SF 750 perhaps?
thank you for the note, but I was thinking of designing a custom case ( with custom dimensions ) so I think it would be manageable if I want to increase the size a little to have 2 cards together especially if I used 2 slots cards