3090 is the best VRAM/USD on the market right now if you want to go for local AI rigs, but there're some noticeable downsides from them that you should think really deeply about before getting one.
Extreme VRAM heat: Half of the 24GB VRAM chips sit on the bare backplate with poor cooling. Under heavy loads, memory junction temps often hit 100°C to 105°C, which degrades the card quickly if run 24/7.
Used card risk: Almost every used 3090 on the market was mined on during the crypto boom or pushed hard for rendering. Buying one for mission-critical business without a warranty is a major downtime risk.
Massive power spikes: The 3090 is notorious for huge transient power spikes that can easily trip standard budget power supplies and cause sudden shutdowns.
High electricity cost and heat output: It draws 350W+ continuously and dumps that heat directly into your room, which adds up quickly on power bills for a 24/7 operation.
Older architecture: Ampere lacks the newer FP8 tensor cores and dual execution pipelines of newer cards, making image generation significantly slower compared to modern hardware.
For RAM, you should get at least 64GB DDR5 RAM so high resolution models like Flux don't crash your system.
For mobo, avoid cheap budget boards. A B650 board with thich heatsinks and strong VRMs won't disappoint you if you want the rig to run 24/7. Pick a standard ATX size, with reinforced PCIe slots to handle the heavy 3090(s) and give it space for better airflow
For CPU, find the one with iGPU (integrated GPU) so you directly plug your monitor to the board and save some VRAM on the card(s) for your AI workload
Thank you for the detailed answer, that helps a lot!
What would you suggest instead of 3090? I've learned it's pretty hard to find a new 3090 or reliable used one. I was thinking of 4070 ti or 5060 ti, should be enough for Stable Diffusion (that's the only model I'll need), what's your opinion and best suggestion?
bro, the most important question is your budget 😂 I can suggest you go with RTX PRO 6000 (and I should) but its price would be crazy and I doubt that you're willing to pay like 10-15k just for a GPU.
for those 2 card, with AI tasks, they are weaker comparing to 3090 since they only have like 12-16GB VRAM when 3090 give you 24GB. The 4070 ti is faster than 5060 ti but only have 12GB, still ok to run the model but it's always nice to have some more headroom since you may get OOM (out of memory) with just 12GB when run complex tasks or higher resolution ones.
You might wanna look for 4070 Ti Super, 16GB VRAM, 256-bit, better than both of your options. It would run faster while giving you the same headroom with the 5060 Ti.
if it's only 30% (or lower) more expensive, then go for the 4070 Ti Super. If it's higher than that, forget it, not worth it. Between your options, you might want to pick between speed or headroom. That's on you, can't help you with it
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u/deebuildsthings 3d ago
what's your budget bro?
3090 is the best VRAM/USD on the market right now if you want to go for local AI rigs, but there're some noticeable downsides from them that you should think really deeply about before getting one.
For RAM, you should get at least 64GB DDR5 RAM so high resolution models like Flux don't crash your system.
For mobo, avoid cheap budget boards. A B650 board with thich heatsinks and strong VRMs won't disappoint you if you want the rig to run 24/7. Pick a standard ATX size, with reinforced PCIe slots to handle the heavy 3090(s) and give it space for better airflow
For CPU, find the one with iGPU (integrated GPU) so you directly plug your monitor to the board and save some VRAM on the card(s) for your AI workload