So i want to buy a Nvidia rtx 3090, could someone tell me if it matters which type you buy if you also want to mine altcoins with it? Or give some tips?
If you want to buy a RTX 3090 be aware that it consumes a lot of power. If you mine ETH it consumes around 290W at 121 MH/s so if you want to have a mining rig with 6 X RTX 3090 then you'll need to buy at least 2 PSU of 1300 W so it's much more expensive.
Compare to that, you can have 6 X RTX 3070 with only one 1300W PSU because each 3070 consumes around 115W at 62 MH/s on Ethash.
Also considering presently (May 21th) you can get a RTX 3070 on Ebay around 1,575 USD and for the
RTX 3090 it's more around 3,975 USD - 4,150 USD.
So as you can see the RTX 3090 is more than twice the price of the RTX 3070 but in fact on Ethash the RTX 3090 is (in average) not more than twice the hash rate of the 3070. So in my opinion the RTX 3070 is a better investment to mine ETH also the efficiency (hashrate per watt) is better with the RTX 3070. Here's a link to the topic I started about that on bitcointalk:
https://bitcointalk.org/index.php?333931.0
except he can buy a 3090 now. my card is set to 284 watts and does 113 mh steady quiet and easy
this is the 2 of them
What do you mean philipma1957 when you wrote : "except he can buy a 3090 now?".
You can buy RTX 3070 on Ebay or Amazon.
Furthermore your RTX3090 does 113 mh which is not even half of the 62.37 mh of the RTX3070.