I think I can fix the RTX 4090 - Undervolting for big gains!

a thousand Watts that is the recommended power budget for this GeForce RTX 4090 from MSI in this economy no wonder gamers are outraged what if I told you there's another way what if I told you I'm gonna ditch my thousand watt power supply and run this top spec gaming rig complete with RTX 4090 on just a 550 watt power supply there will be trials oh crap there will be tribulations ah crap but I will be darned I say if I'm gonna have you guys paying full price to run your rig after you gone wisely blew your savings on a video game machine smart deploy powered by pdq.com smart deploy maintains drivers for you with over 1500 driver packs to choose from deploy any business class device with a single windows image get your free licenses worth over 500 at smartdeploy.com Linus so first things first do you even need a thousand watt power supply or is this whole thing overblown to find out we've dusted off our Nvidia PCAT an inline power measurement device designed for gpus and we've yanked together a pcie y power splitter to accommodate the four bloody eight pin PCI Express connections that you need for the 12 pin adapter for this GPU you see the PCAT was designed in the before four times when nobody ever thought you'd need more than three eight pin power connectors for a single graphics card I wouldn't describe this as our most stable GPU ever but I don't think it's going anywhere there are a couple of ways that we're going to monitor our power consumption first of all we've got the PCAT that I just mentioned before tells us the gpu's power draw then we're going to have a regular wall power meter which is going to tell us the total power draw of the system including any losses due to the inefficiency of our power supply we'll kick things off with a real game in this case cyberpunk 2077 running at 4K mostly High presets with Ray tracing set to medium and our GPU is sucking back a whopping 430 to 470 Watts with our total system power consumption at about 600 watts all while running at a cool 50 FPS boy is this ever a demanding game almost as demanding as msi's combust or stress testing application wow it's a little lower even I guess any additional load that combustor puts on the traditional restaurant rendering course is more than made up for by the activation of the ray tracing cores in cyberpunk we're going to need Ray traced freaking stress tests what the heck whatever the reason it's pretty clear that we don't need a thousand watt power supply to run this card which makes sense I guess given that Nvidia themselves only recommends an 850 watt unit for their Founders Edition version of the 4090 which raises the question why is MSI asking you to spend extra money on a thousand watt power supply if I had to guess I'd say it's for two reasons first to accommodate for any extra power drop from overclocking and second to account for our connected peripherals like bus powered USB devices hard drives LED strips the last thing they want is for you to plug a bunch of other stuff in and then come crying to them when your system shuts down which raises the question how much more power could we draw in their OC load as advertised system power consumption is up in the neighborhood of around 10 percent but unfortunately it didn't have the impact on FPS that I might have expected we've gone from about 50 fps to anywhere from 50 to 54. which kind of raises the question has Nvidia already got the 4090 absolutely redlined and if that is the case could we maintain nearly the same performance but drop our voltage for a big bump in efficiency the first step in our journey is to drop back down to default mode shut down the system and try again with msi's minimum recommended power supply and 850 watt Tech tip for you guys you should never do what I'm doing where you swap out a power supply and use the same modular cables and the reason that you shouldn't do that is because they might not actually use the same pin outs and you can accidentally fry the devices on the other end in our case we have a painstakingly validated that these use exactly the same pin out but we still don't recommend it do as I say not as I do ah no no just kidding it's fine even within the same manufacturer they're not always the same pinout as expected our performance is identical with our 850 watt power supply as is our system power consumption at around 630 Watts from the wall meaning that it is probably safe to run pretty much any 40 90 on a good quality 850 watt power supply and that thousand watt recommendation seems to be more about butt covering than any actual concern for over current protection kicking in and shutting off your computer but if 850 watts is fine then perhaps 750 watts is also fine I mean it still only says 600 watts from the wall right and that's accounting for the power supply is inefficiencies something like 550. I think we're going to get there if these Donuts in the middle of the intersection or anything to go by 750 watts is fine just fine with a 100 plus watt buffer but that's not to say that every 750 watt power supply is going to handle a ryzen 7000 and a 40 90. there are a couple of major factors to consider first is transient spikes we first noticed this with the RTX 3000 Series but Power hungry gpus like this one can momentarily draw far more power than what they are rated for it's not for long enough to cause thermal problems like usually only for a few microseconds but it can be enough to trigger the over current protection of your power supply especially if you're running an older unit that wasn't designed for modern Beast gpus another Factor we're not considering here is capacitor aging this power supply probably only has a dozen or so hours on it at most give it another hundred thousand hours and depending on factors like how hot or cool it was running it could be operating at maybe 95 percent of its brand new capacity or 90 or even much lower by choosing a properly spec unit with plenty of Headroom you give yourself a better chance of years of trouble-free operation and help avoid blade catastrophic failure because the thing about power supplies is when they pop they can sometimes take everything else with them which won't stop us from seeing how low we can go where's my 650 watt power supply I know where it is I'll get it now we are running into a situation where we've actually run out of eight pin power connectors coming out of our power supply so we're going to have to employ a splitter all the Y splitters you know why Splitters like sorry see Sonic you guys were a great sponsor I apologize in advance for blowing up your power supply on camera hopefully we can work together again in the future it's probably fine what will probably happen is we will trigger the over current protection of our power supply and the system will just shut off we do need to drive around a bit before we say for certain this is working it puts a little bit more load on the GPU I saw it at 6 20 there basically we could put a couple LED strips on this system and it could put us over the limit for those of you wondering by the way we stopped using combustor because the load wasn't even as high as cyberpunk I thought it would be higher oh one thing we could do is we could put a little bit of CPU load on the system cyberpunk is still running in the background and what will probably happen is the game I will die in the background and it won't actually be rendering 567. 740 oh get this Brandon how is it doing that that doesn't seem right see Sonic hello our FPS is n a we've left this plane of existence behind GeForce experience this probably just bugs that happens sometimes but I was um I was not expecting this I guess it could be that their 650 watt unit is simply over specked and they set their over current protection for something far in excess of 650 Watts the fan isn't even spinning see Sonic what you doing I mean that is the way to build a really high quality 650 watt power supply is if it's just a 750 watt power supply in you know with the seven scratched out and just put a six there to be clear I'm not expecting anything to happen at the desktop we're sitting at like 130 Watts right now but I am expecting something to happen because aside from going down from 650 to 550 Watts we're also stepping down from csonic's Prime titanium premium power supply lineup to their focus lineup which is that means 80 plus gold it still see Sonic 10-year warranty blah blah blah but it's very unlikely that that's you know an 800 watt power supply and 550 watt clothing holy ah this is not what I expected we are drawing 630 Watts from the wall the GPU is at 450 Watts you know we shot the intro for this video with the trials and the tribulation I was expecting there to be crashes for us to cut in there I'm gonna have to oh oh crap well there's one ah but it's okay we have a way around it first up in our bag of tricks instead of turning our power Target up we are going to turn it down maybe 90 is enough to get by with 550 Watts about 2 800 megahertz is what we get on this one in default so as long as we're close to that we are in good shape we'll also be able to tell from the FPS the game is running at though ah crap well we're gonna need more than uh 10 power limit how about 80 600 watts from the wall already okay come on come on come on come on ah crap come on we're not defeated yet though we found we can go as low as about 70 power limit without losing a ton of performance we make it 70 percent ply overall system power consumption is under 550 watts of the wall crap crap we couldn't even get the close-up but we aren't defeated yet we could drop the GPU down to 60. 50 power limit the issue is that when we do that we risk seeing some pretty funky Behavior even if our FPS still looks okay we might need to start attacking this from a CPU perspective oh crap oh this is not good actually before we adjust our CPU one thing we can try is remember how I'm running a y Splitter from one of my power supply outputs to two of the inputs on our Nvidia power measurement board well there's a way that we could not do that we have four total outputs on this power supply and what we could do is we could just run a single eight pin to the CPU and then three dedicated eight pins over to this board I'm going to step it back to 80 power limit I believe we were overloading a 12 volt rail not actually overloading the power supply oh God it's already okay darn it Brandon you've captured plenty of the crashes so far you don't need to have all of my failures on film oh crap oh crap ah crap I'm just gonna power straight into it 70 power limit let's go yeah it's still jumping up as high as like 360 Watts that doesn't seem like 70 percent of the power limit we're not done yet my hope is that we can save a bit of our overall system power budget by reducing the voltage to our CPU we're leaving everything else on normal we've even got PBO Precision boost overdrive still enabled which allows the CPU to Turbo up higher and for longer but maybe by reducing the voltage just just 0.15 volts get away with something here we might have gone a little aggressive on that CPU underbolt but we also really want to see this work so go in game in game we managed to drop our overall system power consumption by like 20 and all it cost us was we're running at 49 FPS right now 48 less than 10 percent of our actual real world performance we are running a 7900x and a 4090 on a 550 watt power supply as promised even though I didn't know for sure what happened of course as cool as that was nobody's gonna buy a GPU like this only to leave performance on the table thankfully you can have the best of both worlds we observed that our GPU clock was around 2.8 gigahertz under sustained load so what we can do is go into the curve editor in MSI afterburner hold alt and take our very farthest dot here and drag our frequency Target down to about 2.8 then we're going to individually drag up our 950 millivolt dot to 2.8 gigahertz and a plus changed our Target from 3 gigahertz to 2.8 which is fine because we were only hitting 2.8 gigahertz anyway theoretically assuming we stay stable we should have our lower power consumption and our stock performance almost we'll get to that in a moment the key night among you will have noticed we're back to our 650 rather than our 550 watt power supply we saw some very strange Behavior with the 550. so for this demo I just want to show you how the power consumption is low I don't need to be using a 550 watt power supply the game Crash let's try 970 millivolts and there we have it even though we backed off our CPU under volt a little bit we're down to minus 0.1 volt and we're at 975 millivolts on our GPU we are still 100 Watts lower than we were when we started as for our performance lower but we can fix that very easily all we got to do is alt Tab out then we're just going to play with our memory clock let's try plus 500. it's possible we could go higher than that but 500 is pretty safe now we're back in game and I'm seeing as high as 60 FPS but going back to the same area now it's more like yeah dropped under 50. ah let's give the memory a little more juice let's say 900. 40 Watts 52 54. 60 say we are pretty darn near we started now not bad for a 650 watt power supply all of this raises the question what if instead of going full balls out Nvidia did what we did we could have had smaller coolers more sensible power supply requirements nearly the same performance like in real terms that could be hundreds of dollars in savings over the years that you might be expected to run a GPU like this but then it's also possible that nothing would have been different maybe in order to get economical yields on Ada Lovelace RTX 4000 architecture code name they needed to accept these power hungry parts and maybe we just got a good one the good news though is that even if that's the case at sixteen hundred dollars this is a problem that won't affect a lot of people and those that can't afford this GPU can probably afford the running cost either way it was an interesting Adventure just like this interesting Adventure into Segway land ahoy it's our sponsor wealthfront thanks wealthfront for sponsoring this portion of today's video does anyone know what's going on with the economy right now no really though anyone inflation keeps inflating and who knows if we're in a recession at the moment but it's always a good time to save and well friend is the app for making the most of your savings right now you can earn 2.55 apy with a wealthfront cash account so if you had twenty five thousand dollars in a wealthfront cash account you'd be on Pace to earn about 637 dollars by year end that's a whole steam deck their cash account lets you avoid the risk of loss that comes with investing in the 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Channel: Linus Tech Tips

Views: 1,799,835

Keywords: GPU, PSU, Power Supply, RTX 4090, Undervolt, GPU Undervolting, Power Consumption, RTX 4090 recommended PSU, 1000W power supply, undervolt RTX 4090, RTX 4090 750W, RTX 4090 650W, RTX4090, RTX 4090 550W

Id: yU4CFhtS95Q

Length: 18min 2sec (1082 seconds)

Published: Tue Oct 25 2022

Reddit Comments

[u/CornGun]

It seems like he just plays Cyberpunk for 5 minutes to test power draw. Which is fine if the point of the video is to be more entertainment than educational.

Some more rigorous testing to look into sustained peak loads and transient power spikes would have been more helpful and interesting in my opinion. But when you have to pump out so many videos this is what happens I guess.