I've got a Legion T5-28IMB05 Desktop (Lenovo) - Type 90NC PC with a GTX 1660 SUPER graphics card in and I want to upgrade it to a EVGA RTX 3080 FTW3 10G-P5-3897-KL, 10GB GDDR6X, LHR and I don't know how to go about doing this because I don't know too much about PC upgrading and I am not sure If I will be missing something to be able to finish the upgrade and so I need someone to give me some feed back on what I should get for this upgrade.

platform specs Link https://psref.lenovo.com/Product/Lenovo_Legion_T5_28IMB05?tab=spec

- if you want to install an RTX 3080, it is possible, but you must consider the following :
[ RTX 3080 has a Gen 4 interface and your PC has a Gen 3 interface slot, which means that the RTX will run with Gen 3 limitation
[ your PC has a 400W or 650W power supply, and this must be changed to a minimum 750W supply that necessarily has three 8-pin connectors to power the RTX graphics card

[ the RTX 3080 must fit in your PC case / you have to check / see that I have also put the dimensions of the RTX 3080 graphics card below in images

edit :

if the RTX 3080 does not fit, i.e. it is too long for your PC, then you can see the following recommendation below :

- my recommendation if you have a 650W power supply in your PC, is to buy an RTX 3060, because you no longer need to make changes to your system
[ below you have a link with an RTX 3060 as an example

RTX Link https://www.amazon.com/ASUS-DisplayPort-Axial-tech-Protective-Auto-Extreme/dp/B09CBS8ZF3?th=1

- I looked on Lenovo's website for parts for the RTX 3070, but at the moment they don't have them in stock :

Lenovo Link https://lenovo.encompass.com/modelbrowse/LEN/2/2

Parts Lookup
https://support.lenovo.com/partslookup?cid=all:apps:hxatlt

Pcie gen3 vs gen4 is not such big difference to care.

U only need strong enought PSU (at least 750W), and UR good to go.

About size: I have 26iob6, which is smaller than 28imb05, and I've recently upgrade to Asus TUF 3080, which is similar in size, so EVGA should fit.

Only concern is your cpu: If you have i5 and game in 1080p than 3080 won't be fully used.

@jagoooodka wrote:

Pcie gen3 vs gen4 is not such big difference to care.

... I have 26iob6 ... and I've recently upgrade to Asus TUF 3080 ...

- you're right, I just wanted to mention that the graphics cards are different
[ in current AAA games the differences are up to 3% in favor of Gen 4

- can you post a picture of your system so I can see how much space is left with the RTX graphics card?

There is about 1-1,5cm space to front fan.

Good enought maybe, but if I were U, than I'll look for non Lenovo parts (they R usually overpriced). I bought full modular MSI MPG A850GF new under 90$ (when pc parts cost more in my country than in US)...

Also Lenovo GPU is not bad, but for the same price U can have EVGA or Asus card, which means better cooling, better vbios (even two), higher power limit and higher performance. 

But decision is of course yours :-)

Thanks! I think I’ll stay with the 2 stuff that I linked, just to be safe.

@jagoooodka wrote:

There is about 1-1,5cm space to front fan.

- super 
thanks