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Building an AI server on a budget

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Re: Building an AI server on a budget

#21
post #9

In January 2024 there was a similar post ( https://news.ycombinator.com/item?id=38985152 ) wherein the author selected dual NVidia 4060 Ti's for an at-home-LLM-with-voice-control -- because they were the cheapest cost per GB of well-supported VRAM at the time. (They probably still are, or at least pretty close to it.) That informed my decision shortly after, when I built something similar - that video card model was…

> which implies the hubris of a North American

No need for that.

Re: Building an AI server on a budget

#23

If the author is reading this I'll point out that the cuda toolkit you find in the repositories is generally older. You can find the latest versions straight from Nvidia: https://developer.nvidia.com/cuda-downloads?target_os=Linux&... The caveat is that sometimes a library might be expecting an older version of cuda. The vram on the GPU does make a difference, so it would at some point be worth looking at another GPU…

The other main caveat is that installing from custom sources using apt is a massive pain in the ass.

Re: Building an AI server on a budget

#24

Whenever I get to a section that was clearly autogenerated by an LLM I lose interest in the entire article. Suddenly the entire thing is suspect and I feel like I’m wasting my time, since I’m lo lingering encountering the mind of another person, just interacting with a system.

Eh, yeah - the article starts off pretty specific but then gets into the weeds of stuff like how to put your PC together, which is far from novel information and certainly not on-topic in my opinion.

Re: Building an AI server on a budget

#26
Someone posted that they had used a "mining rig" [0] from AliExpress for less than $100. It even has RAM and a CPU. He picked up a 2000W (!) DELL server PS for cheap off eBay. The GPUs were NVIDIA TESLAs (M40 for example) since they often have a lot of RAM and are less expensive.

I followed in those footsteps to create my own [1] (photo [2]).

I picked up a 24GB M40 for around $300 off eBay. I 3D printed a "cowl" for the GPU that I found online and picked up two small fans from Amazon that got int he cowl. Attached the cowl + fans keep the GPU cool. (These TESLA server GPUs have no fan since they're expected to live in one of those wind-tunnels called a server rack).

I bought the same cheap DELL server PS that the original person had used and I also had to get a break-out board (and power-supply cables and adapters) for the GPU.

Thanks to LLMs, I was able to successfully install Rocky Linux as well as CUDA and NVIDIA drivers. I SSH into it and run ollama commands.

My own hurdle at this point is: I have a 2nd 24 GB M40 TESLA but when installed on the motherboard, Linux will not boot. LLMs are helping me try to set up BIOS correctly or otherwise determine what the issue is. (We'll see.) I would love to get to 48 GB.

[0] https://www.aliexpress.us/item/3256806580127486.html

[1] https://bsky.app/profile/engineersneedart.com/post/3lmg4kiz4...

[2] https://cdn.bsky.app/img/feed_fullsize/plain/did:plc:oxjqlam...

Re: Building an AI server on a budget

#27

With system builds like this I always feel the VRAM is the limiting factor when it comes to what models you can run, and consumer grade stuff tends to max out at 16GB or (somemtimes) 24GB for more expensive models. It does make me wonder whether we'll start to see more and more computers with unified memory architecture (like the Mac) - I know nvidia have the Digits thing which has been renamed to something else

Go server GPU (TESLA) and 24 GB is not unusual. (And also about $300 used on eBay.)

Re: Building an AI server on a budget

#28
post #14
post #11

I thought prevailing wisdom was that a used 3090 with it's larger vram was the best budget gpu choice? And in general, if on a budget then why not buy used and not new? And more so as the author himself talks about the resale value for when he sells it on.

> I thought prevailing wisdom was that a used 3090 with it's larger vram was the best budget gpu choice? The trick is memory bandwidth - not just the amount of VRAM - is important for LLM inference. For example, the B50 specs list a memory bandwidth of 224 GB/s [1], whereas the Nvidia RTX 3090 has over 900GB/s [2]. The 4070's bandwidth is "just" 500GB/s [3]. More VRAM helps run larger models but with lower bandwidth…

> The trick is memory bandwidth - not just the amount of VRAM - is important for LLM inference.

I'm not really knowledgeable about this space, so maybe I'm missing something:

Why does the bus performance affect token generation? I would expect it to cause a slow startup when loading the model, but once the model is loaded, just how much bandwidth can the token generation possibly use?

Token generation is completely on the card using the memory on the card, without any bus IO at all, no?

IOW, I'm trying to think of what IO the card is going to need for token generation, and I can't think of any other than returning the tokens (which, even on a slow 100MB/s transfer is still going to be about 100x the rate at which tokens are being generated.

Re: Building an AI server on a budget

#30
For $100 more you could get a used 3090 with twice as much VRAM. You could also get 4060 Ti which is cheaper than 4070 and it has 16 GB VRAM (although it's less powerfull too, so I guess depends on the use case)
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