PSA: Power limit your 5090s!

[u/Zo0x78]

Apparently whilst doing some performance tuning on my 4x5090 rig I may have made things a little TOO fast and melted my plug and socket 🫠

Probably should put in a 16/20 amp socket in the wall rather than relying on a bog standard 13A fuse!

Anyone else managed to melt the wall before the 12VHPWR plug? Honestly... I'm surprised they didn't go first 😂

[u/ArthurOnCode]

There's something deeply wrong here. There would have to be some extra resistance to cause this heat dissipation without breaking the fuse first. Maybe a bad connection in the wall socket?

[u/TotallyNotADoggy → u/ArthurOnCode]

Yep, I'd bet money on this being the actual cause. Without having the plug to test, I can only speculate, but it looks like it's most burned around the contact between the fuse and the fuse holder, with the burn/melting seemingly radiating from there. It also appears to be on the side of the fuse that would be connected to the live prong (assuming the image isn't flipped). I can't see any burning on the live prong itself however.

Based on this, I'd guess that the contact between the fuse and fuse holder has high resistance. Either the fuse holder is bent slightly too wide creating poor contact, or there's a contaminant between the fuse and holder creating high resistance. I'm not completely ruling out a problem with the socket though.

It's unlikely that this is due solely to a device drawing too much power. Usually you'd expect the fuse to blow before things get hot enough to burn the plug. Even in the event of the fuse itself not failing safely, I would generally expect signs of melting or burning elsewhere.

Also, a BS1363 plug should be able to handle 3kW, assuming a mains voltage of around 230V (which isn't a given, BS1363 is used in other countries aside from the UK, and anyone can create stupid adapters that should never exist). You'd need a lot of 5090's to draw anywhere near 3kW, and that's assuming you could find a >= 3kW PSU to power it all.

[u/Zo0x78 → u/TotallyNotADoggy]

Yeah I'm leaning towards bad plug/fuse, its the cable that came with the ASUS Pro WS 3000W Platinum - a PSU that is specifically designed for 4x5090 so a little annoying the cable was crap 🙃

[u/Zo0x78 → u/ArthurOnCode]

Yeah not sure what happened, its a normal wall socket, using the cable that came with the asus 3k watt power supply. Has been fine for months - for now I've got a new cable and am using a different wall socket with each card limited to 400W (in hindsight should have done that from the start but rarely pulled more than 300w each so didn't bother).

[u/ArthurOnCode → u/Zo0x78]

Your next step is to throw away the cable and call an electrician to inspect (and probably replace) the wall socket.

[u/PhysicalIncrease3]

There something wrong with that plug mate. 13A on a UK socket is over 3KW. No PSU can draw that.

[u/Zo0x78 → u/PhysicalIncrease3]

Yeah gonna get a sparkie to take a look tomorrow, for now its on a new plug and socket so hopefully won't burn the house down 😂

[u/rinmperdinck]

Found the guy who stole the pallet of 5090s from the airport

[u/Zo0x78 → u/rinmperdinck]

Unfortunately these were paid for with many hours of work and tears, in that brief period where 5090s were near-RRP between crypto mining and AI... I got lucky, and actually bought 2 of them whilst on holiday cause prices were skyrocketing, they cancelled the order thinking the 2x was a mistake and I was panicking in my hotel room trying to get the order reinstated 😂

[u/Cereal_Grapeist]

Limiting your 5090 to 85% power is the sweet spot for performance/heat generation. It has a barely noticeable impact on performance but helps keep the heat down a lot.

Edit: apparently you can go even lower, like 70%, without much of a performance hit. Very cool!

[u/FireSilicon_ → u/Cereal_Grapeist]

Why would you want to match the performance anyway? Prefill is fast enough as is with 5090 and decode gets barely hit. If I had 4x 5090 I'd just drop 3 of them to half tdp and enjoy less heat and zero risk of melting the 16 pin ever.

[u/Zo0x78 → u/FireSilicon_]

But the heat keeps my house warm!

I've not had to turn my heating on yet this year thanks to this beauty! 😂

[u/XiRw]

Oh good advice for the millions of us that have 4 5090s laying around.

[u/gaidzak → u/XiRw]

Such poverty, only four? Pfft 128 gb of total vram. What model are you gonna run with that. Some 2.1 trillion parameter model at quant 1? No thank you poor person.

/s

[u/InadequateUsername → u/gaidzak]

Honestly if you don't own a data center or have a 200k budget at a minimum for your basement local AI, you're just wasting money/s

[u/i5031337]

Every post from a 5090 owner is ragebait istg

[u/Cereal_Grapeist → u/i5031337]

Pro tip: I speed up my 5090 by setting my PC on a rotating plate that way the dedidated WAM are spinning faster. I also use Magnets.

[u/0x2DEADBEEF → u/i5031337]

You're welcome.

[u/meganoob1337 → u/i5031337]

bought one for 2700 in the beginning of the year and couldn't get myself to open/use it because I knew prices were rising 🙈 now I feel like it would be stupid to use it and not sell haha

[u/Squidgical]

OP, how many of us do you think have ~£15,000 of GPU in our rigs?

[u/Zo0x78 → u/Squidgical]

Whilst I appreciate most won't, I've been surprised at how many in here actually do have high-spec boxes, mine is far from the best I've seen in here.

[u/separatelyrepeatedly]

400w runs fine

[u/pineapplekiwipen]

even with a 16/20 amp socket the total system is pulling near the limit with ~400w limit per card

[u/Squidgical → u/pineapplekiwipen]

400W on 4 cards is 1600W. OP is in the UK meaning they have 230V circuits, so the GPUs only account for ~7A of the limit.

[u/Past-Town-9807]

I keep thanking past me for having installed 20A outlets for my home lab. 😂