Question on PSUs

[ThoRob]

I understand the argument for future proofing the PSU as the upgrades are generally quite cheep however I am struggling to understand some of the recommendations. (used what PSU.com for PSU required but it seems to match what other sites are recommending).

Mid range system

CPU	TDP	GPU	TDP	Total TDP	PSU Required
12600k	125​	3060 ti	200​	325​	550​
11600k	125​	2060 S	175​	300​	550​
10600k	125​	1660 S	125​	250​	500​

High end System

CPU	TDP	GPU	TDP	Total TDP	PSU Required
12700k	125​	3080 ti	350​	475​	700​
11700k	125​	2080 ti	250​	375​	600​
10700k	125​	1080 ti	250​	375​	600​

People seem to be recommending 850W PSUs for mid range systems and 1000W for High end.
However assuming most people skip 1 generation and only update there CPU & GPU once before getting a new PC this seems to be going a bit overboard.
I would have though 650W for a mid range system and 850W for a high end system should be plenty allowing for upgrades within the life of the PC.

So my question is who on here has had to replace there PSU in the past (other than for failure) and under what circumstances? (What PSU CPU and GPU did you have and what were you upgrading to?)

Edit: I realize max power (especially for modern CPUs) is somewhat higher than TDP but I believe this is already accounted for in the PSU required figures.

 

[SpyderTracks]

I understand the argument for future proofing the PSU as the upgrades are generally quite cheep however I am struggling to understand some of the recommendations. (used what PSU.com for PSU required but it seems to match what other sites are recommending).

Mid range system

CPU	TDP	GPU	TDP	Total TDP	PSU Required
12600k	125​	3060 ti	200​	325​	550​
11600k	125​	2060 S	175​	300​	550​
10600k	125​	1660 S	125​	250​	500​

High end System

CPU	TDP	GPU	TDP	Total TDP	PSU Required
12700k	125​	3080 ti	350​	475​	700​
11700k	125​	2080 ti	250​	375​	600​
10700k	125​	1080 ti	250​	375​	600​

People seem to be recommending 850W PSUs for mid range systems and 1000W for High end.
However assuming most people skip 1 generation and only update there CPU & GPU once before getting a new PC this seems to be going a bit overboard.
I would have though 650W for a mid range system and 850W for a high end system should be plenty allowing for upgrades within the life of the PC.

So my question is who on here has had to replace there PSU in the past (other than for failure) and under what circumstances? (What PSU CPU and GPU did you have and what were you upgrading to?)

Edit: I realize max power (especially for modern CPUs) is somewhat higher than TDP but I believe this is already accounted for in the PSU required figures.

Firstly, the above is a "Bad" PSU calculator, it doesn't take into account any kind of overclock. TDP is irrelevant in todays metrics, that calculator isn't taking into account actual wattage consumption. Also, you would never spec 20% headroom unless you were on a really strict budget, or it was a basic office PC or something. Normally you'd want max load at around 60%. Furthermore, TDP valuations of GPU's tend to be set by Founders Editions, and FE's will almost always use less power than aftermarket solutions.

Again, if you're speccing PSU's to your current setup, then you're doing it wrong. We would never spec a GPU to the current system.

The next gen PSU's are able to draw 670W just for the GPU, and aftermarket cards will always draw far closer to the limits. Current CPU's will happily pull over 400W overclocked.

Intel Core i9-12900K Overclocked To 5.3 GHz Across All Cores With 1.44V Voltage, Hits Insane 400W Power Consumption In AIDA64 Stress Test

Intel's Core i9-12900K Alder Lake CPU has been overclocked to 5.3 GHz across all cores and consumes an insane 400 Watts of power.

wccftech.com

You also never want a GPU to "cover" the system, the higher headroom you have, the less it has to throttle, the better efficiency and in semi passive / passive units like the RMx, then the quieter because the fans aren't kicking in.

 

[sck451]

Here's a pair of graphs from the Corsair RMx manual:

https://www.corsair.com/corsairmedia/sys_master/productcontent/RMx_2018_Manual.pdf (It's worth comparing the other power ratings to see how the values change going down the product stack.)

Clearly you don't really want to be speccing your power supply to be working mostly towards the top of its capacity: you want it running in its most efficient and quiet range.

 

[DarTon]

The economics of choosing a PSU are reasonably easy to think about.

Let's say you need a 750W PSU right now but think there is a 50% chance that you might need a 1000W in the three years time (that 6080 drawing 550W will look just too lovely). Resale value for the 750W is 50% of what you paid for it. With the RMx750 at £107, the breakeven price for the 1000W RMx PSU is £149. It's currently £138, so it's rational to buy it.

Now my assumptions are subjective but you can see that even if you do just one GPU upgrade over the lifetime of the PC, it's probably sensible to bump up the PSU to some degree on the initial purchase. Something like the HX1200 at £199 is much harder to justify because the price increase is so much larger. You need to be very confident you will need the extra power. For someone who want the PC to last 10 years it might be economically senisble. For someone who wants it to last 5 years, very unlikely.

Now economics aren't the only driver. Something like a draw of no more than 60-65% is also optimal for both efficiency and noise. It's not just about the wattage either; it's also about the quality. Quality will impact the stability of the power supply as it tends toward it's capacity limit. It's very different drawing 700W from an RMx 750W PSU than 700W from a CV 750W.

 

[Scott]

This is one of my bug bears right now. PSU calculators just haven't shifted with the nomenclature in their powered brethren.

The above absolutely encapsulates any reasoning and it's something that I've always put forward when suggesting any builds. Many moons ago I had many a spirited discussion on here as I was always in favour of forward planning & future proofing some elements. At the time the argument returned was that future proofing was a myth, and to a certain extent it is, but I have built my case over the years that certain elements can and should be chosen with future use in mind. The building blocks or the foundation of the systems. Parts that are universal across any and all chipsets or branding choices.

I've always had way more power in the PSU department than I required. My current build has a 750w RM PSU in it that I bought before I even had a GPU in the system. I'm not exactly sure how old it is but the x variant didn't exist when I bought it. My guess is it would be 9 or 10 years old and I've only had a GPU since 2019.

Alas I didn't future proof enough as the 1000w option was just a touch too far at the time (you can imagine the prices back then) and I would have massively under-utilised it for 6 years so that would likely have been diminishing returns.

My next PSU will most definitely be at least a 1000w offering though, potentially up to 1200w, as I'm planning to see out the next 10 years of upgrades and usage with it in place.

 

[Scott]

The economics of choosing a PSU are reasonably easy to think about.

Let's say you need a 750W PSU right now but think there is a 50% chance that you might need a 1000W in the three years time (that 6080 drawing 550W will look just too lovely). Resale value for the 750W is 50% of what you paid for it. With the RMx750 at £107, the breakeven price for the 1000W RMx PSU is £149. It's currently £138, so it's rational to buy it.

Now my assumptions are subjective but you can see that even if you do just one GPU upgrade over the lifetime of the PC, it's probably sensible to bump up the PSU to some degree on the initial purchase. Something like the HX1200 at £199 is much harder to justify because the price increase is so much larger. You need to be very confident you will need the extra power. For someone who want the PC to last 10 years it might be economically senisble. For someone who wants it to last 5 years, very unlikely.

Now economics aren't the only driver. Something like a draw of no more than 60-65% is also optimal for both efficiency and noise. It's not just about the wattage either; it's also about the quality. Quality will impact the stability of the power supply as it tends toward it's capacity limit. It's very different drawing 700W from an RMx 750W PSU than 700W from a CV 750W.

As much as the financial decision is often at the forefront of the consumers mind, they often don't consider the implications of a PSU upgrade.

IMO a very small % of PCS customers would have the confidence, and perhaps even the skill required, to properly replace a PSU.

Often the costs associated with the upgrade are higher than just the components themselves. Plus the potential stress of it going wrong.

 

[B4zookaw]

In my case, I also considered if I'm likely to be upgrading my build, or replacing it entirely. Given my CPU (5900x) is about as good as you can get on AMD, if I decide to upgrade, it will be to the next gen. So I'll need to replace the MB if I go with Intel and presumably for AMD as well, unless they maintain backward compatability. And that would mean uplift of RAM to DDR5, more Gen4 SSD etc. So it might be easier for me to sell the current build and buy/build a complete new system. And selling the existing build with a PSU and other parts rather than canibalising would be preferably for any buyers I would think.

The same argument might not apply with someone with a mid-level spec of course, as they have room to grow on their current platform.

And we all assume that next gen GPUs will use the same power connection specs as current PSUs? Proprietary 16 pin Nvida GPU power input anyone?

 

[Scott]

Edit: I realize max power (especially for modern CPUs) is somewhat higher than TDP but I believe this is already accounted for in the PSU required figures.

Unfortunately not, this is one of my concerns as it seems to be quite widespread. I'll take one of your examples below:

CPU	TDP	GPU	TDP	Total TDP	PSU Required
12700k	125​	3080 ti	350​	475​	700​
12700k	190(375 OC)​	3080 ti	375-450​	565-825w + Motherboard, Drives, etc (100w) = 665-925w​	798-1100w inc 20%​

Your calculation didn't account for the basic running of the system. Everything needs power, even the cooler. Modern consensus is around 100w for everything being utilised outwith the CPU/GPU. With that in mind it takes you to an 850w PSU as a minimum (which is what we tend to recommend now) with the 1000w being a more optimum choice. For extreme, the 1200w is required, which is also what we recommend for beastly builds.

With the PSU, you want too much rather than too little as you don't want to be working it constantly at it's peak. The efficiency graphs above show where you would want to land with such a PSU.

Also keep in mind that PSUs are not created equal. Corsair are very highly regarded in their PSUs so you know what you are getting. To use a generic brand you would need to consider a much higher power grading as the quality tends not to be there. Getting a clean 800w is so important to performance so the RMx is really the minimum level of PSU that should be considered for mid range +.

 

[Scott]

In my case, I also considered if I'm likely to be upgrading my build, or replacing it entirely. Given my CPU (5900x) is about as good as you can get on AMD, if I decide to upgrade, it will be to the next gen. So I'll need to replace the MB if I go with Intel and presumably for AMD as well, unless they maintain backward compatability. And that would mean uplift of RAM to DDR5, more Gen4 SSD etc. So it might be easier for me to sell the current build and buy/build a complete new system. And selling the existing build with a PSU and other parts rather than canibalising would be preferably for any buyers I would think.

The same argument might not apply with someone with a mid-level spec of course, as they have room to grow on their current platform.

And we all assume that next gen GPUs will use the same power connection specs as current PSUs? Proprietary 16 pin Nvida GPU power input anyone?

Looking at your case in solitude, I think the 750w RMx was about the right choice to be honest (using your logic). Note that you upgraded from 650w when you didn't technically need to, that move alone saves the day IMO. I totally agree that you're likely to replace the system in its entirety based on the socket and chipset, but there's absolutely no reason the 5900X won't be performing very well in gaming for a decade. It's a high end 5ghz (magic number) chip. It has the cores to handle anything that comes through with DX12+ and was a fine choice overall.

The key will be if you do upgrade the GPU to the next generation. If the power is the expected 400w+ then you will be very marginal to keep any sort of margin. Thankfully you have the AMD power efficiency on your side so tier for tier I think you'll eek out a GPU generation upgrade.

I would have suggested 850w to you though, to give you wiggle room.

 

[B4zookaw]

Looking at your case in solitude, I think the 750w RMx was about the right choice to be honest (using your logic). Note that you upgraded from 650w when you didn't technically need to, that move alone saves the day IMO. I totally agree that you're likely to replace the system in its entirety based on the socket and chipset, but there's absolutely no reason the 5900X won't be performing very well in gaming for a decade. It's a high end 5ghz (magic number) chip. It has the cores to handle anything that comes through with DX12+ and was a fine choice overall.

The key will be if you do upgrade the GPU to the next generation. If the power is the expected 400w+ then you will be very marginal to keep any sort of margin. Thankfully you have the AMD power efficiency on your side so tier for tier I think you'll eek out a GPU generation upgrade.

I would have suggested 850w to you though, to give you wiggle room.

Yep, a number of people did suggest 850, but I had to fit the budget at the time, so felt moving 650 TX to 750RMx was a good compromise.
Of course in less than 2 months since getting the PC I've bought:

• 3x Corsair ML120 fans to replace original case fans
• 1x BeQuiet Silentwings V3 to replace exhaust fan
• Individually sleeved GPU cables
• Razer basilisk v3
• Better monitor

Thankfully my bonuses are paid quarterly....

 

[Martinr36]

When I originally did the Berserker spec I put an 850W RMx in it, but it was suggested that I went to the 1000W version for the sake of £19

 

[ThoRob]

Unfortunately not, this is one of my concerns as it seems to be quite widespread. I'll take one of your examples below:



Your calculation didn't account for the basic running of the system. Everything needs power, even the cooler. Modern consensus is around 100w for everything being utilised outwith the CPU/GPU. With that in mind it takes you to an 850w PSU as a minimum (which is what we tend to recommend now) with the 1000w being a more optimum choice. For extreme, the 1200w is required, which is also what we recommend for beastly builds.

With the PSU, you want too much rather than too little as you don't want to be working it constantly at it's peak. The efficiency graphs above show where you would want to land with such a PSU.

Also keep in mind that PSUs are not created equal. Corsair are very highly regarded in their PSUs so you know what you are getting. To use a generic brand you would need to consider a much higher power grading as the quality tends not to be there. Getting a clean 800w is so important to performance so the RMx is really the minimum level of PSU that should be considered for mid range +.

Thanks for the information.

If people are looking to overclock then obviously that has to be taken into account however looking across the forums it seems that more people don't overclock than do.

Where did you get the information for the 3080 ti having a TDP of 375-450? All the information I can find including the manufactures states 350W. If this is the case then my figures would need to be reviewed.

I assumed 35W which is why I had the calculation CPU+GPU = 425W + 100W (rest of system) = 525W + 20% = 690W therefore current requirements = 700W
Looking over the trend for the last few generations 850W seems to allow pleanty of space to upgrade.

For the mid range systems CPU+GPu = 325W + 100W (rest of system) = 425W +20% = 510W current requirements. So again 650 seems ample.

Thanks for the link to fan noise / efficiency data. The variation in fan noise seems to be fairly minimal +/- a couple of db.
I presume the efficiency has an impact on heat generation which might be a consideration although I am unclear as to how much of an impact it would have. However it also shows that specking an 850-1000W PSU if you don't currently have a top of the line system could be costing you more money for the PSU and actually lowering efficiency. In fact assuming that most systems run most of the time at significantly less that 100% TDP load it might not be a good thing for a lot of people.

Apologies if I am being slow to pick things up or if I have missed the point. I am a bit of a nerd and once I get a question in my head I am not good at letting it go. (might come from 20 years working in a technical department)

 

[SpyderTracks]

Thanks for the information.

If people are looking to overclock then obviously that has to be taken into account however looking across the forums it seems that more people don't overclock than do.

Where did you get the information for the 3080 ti having a TDP of 375-450? All the information I can find including the manufactures states 350W. If this is the case then my figures would need to be reviewed.

I assumed 35W which is why I had the calculation CPU+GPU = 425W + 100W (rest of system) = 525W + 20% = 690W therefore current requirements = 700W
Looking over the trend for the last few generations 850W seems to allow pleanty of space to upgrade.

For the mid range systems CPU+GPu = 325W + 100W (rest of system) = 425W +20% = 510W current requirements. So again 650 seems ample.

Thanks for the link to fan noise / efficiency data. The variation in fan noise seems to be fairly minimal +/- a couple of db.
I presume the efficiency has an impact on heat generation which might be a consideration although I am unclear as to how much of an impact it would have. However it also shows that specking an 850-1000W PSU if you don't currently have a top of the line system could be costing you more money for the PSU and actually lowering efficiency. In fact assuming that most systems run most of the time at significantly less that 100% TDP load it might not be a good thing for a lot of people.

Apologies if I am being slow to pick things up or if I have missed the point. I am a bit of a nerd and once I get a question in my head I am not good at letting it go. (might come from 20 years working in a technical department)

You're missing the point about upgrades.

Just because someone picks a midrange card now, in 5 years they may well pick a top of the range card.

Similarly with overclocking. You have to make the assumption that everyone is going to want to overclock.

The point it, people's needs and budgets change over the time they have the PC as it's a substantial time period. You have to allow room in the system for them to be able to make any of those changes in the future.

 

[Scott]

Thanks for the information.

If people are looking to overclock then obviously that has to be taken into account however looking across the forums it seems that more people don't overclock than do.

Where did you get the information for the 3080 ti having a TDP of 375-450? All the information I can find including the manufactures states 350W. If this is the case then my figures would need to be reviewed.

I assumed 35W which is why I had the calculation CPU+GPU = 425W + 100W (rest of system) = 525W + 20% = 690W therefore current requirements = 700W
Looking over the trend for the last few generations 850W seems to allow pleanty of space to upgrade.

For the mid range systems CPU+GPu = 325W + 100W (rest of system) = 425W +20% = 510W current requirements. So again 650 seems ample.

Thanks for the link to fan noise / efficiency data. The variation in fan noise seems to be fairly minimal +/- a couple of db.
I presume the efficiency has an impact on heat generation which might be a consideration although I am unclear as to how much of an impact it would have. However it also shows that specking an 850-1000W PSU if you don't currently have a top of the line system could be costing you more money for the PSU and actually lowering efficiency. In fact assuming that most systems run most of the time at significantly less that 100% TDP load it might not be a good thing for a lot of people.

Apologies if I am being slow to pick things up or if I have missed the point. I am a bit of a nerd and once I get a question in my head I am not good at letting it go. (might come from 20 years working in a technical department)

TDP across mainstream components is now referenced at the peak performance without any sort of overclocking or boost settings applied. All modern day cards & CPUs have the option to boost past their standard clock speeds by default, based on a number of parameters such as temperature etc.

The 3080Ti reference card has a TDP of 350w when not boosting past it's pre-defined stock frequency. When boosting past this stock frequency I believe the power consumption creeps up towards 390w (I've seen 400 mentioned also). I choose 375 as it was a nice break point. When you move onto AIB boards, the boosting limits are widened and the power delivery upper threshold is increased. The FTW3 3080Ti has seen 450w during maximum draw (as an example).

This is not overclocking though, this is simply the manufacturers boosting limits that are pre-determined. When you OC, you can take it to a whole other level on the CPU.... the GPU, not so much without unlocking the BIOS or hardware mods... but anyone doing that already knows what their requirements are going to be.

I'm not sure what you mean by the assumption part. 350w + 125w isn't 425w, it's 475w. + 100w = 575w. + 20% = 690w. But all of that is without any boosting past the stock frequencies. You would be running a 12700k at 3.6ghz without any possibility of going past this frequency to remain at 125w. This is not the design intention of the part, even though Intel will claim it is from a warranty standpoint. At full chat with all stock limits completely intact the CPU can peak at 200w on its own. Factor that into the above calculation and you have hit 780w.

This means that 850w is the minimum that you would safely want in that system. There is just no way 850w would be recommended from a build perspective when 1000w is £19 and covers so much more future scope.

Now factor in the expectations of the next generation of GPU from Nvidia. It's widely reported that the level of the 3080ti is going to be getting quite a hefty power upgrade. The expectation for such a level is 450w (and that may even just be the 4080, although I hope they reign it in).

Factor that into the above calculation:

200w CPU, 450w GPU, 100w misc - 750w + 20% = 900w

At this level of PC I would always actually recommend the 1200w PSU, just to keep you on the playing field for whatever power requirements come with the coming generations while keeping a decent heardroom and working inside a good efficiency curve.

I've said it before, my next build will have at least a 1000w PSU in it, likely a 1200w one. Not because of what I need it for now or next year, but to keep it going as long as my trusty 750w RM has.

 

[DarTon]

My personal machine has got a 3080 Ti FE. At stock, the TDP is 350W but power consumption hits 408W at peak. Similarly, the 5900X has a TDP of 105W but the Package Power Tracking (PPT) setting for that CPU is 142W. I've seen it hit around 140W during use. Assuming just over 100W for other components, my power draw can exceed 650W. I did run this machine on a 750W RMx for a while and it was ok because RMx PSUs are high quality but it was noisy. The 1000W PSU I now have is more appropriate.

My work machine has a EVGA 3090 FTW3 (and an A6000 but we'll ignore that). The TDP of the 3090 is 350W. At stock, power consumption hits around 450W, fully overclocked it's hits the power limit at 525W. The 5950X also has a PPT of 142W. So that system simply couldn't operate with a 750W PSU and even a 850W would be running close to the limit.

On Intel 12th gen CPUs, the Turbo Power Limit (PL2) is up to 2.5x the TDP. Hence why you see 12900K taking up to 400W.

The point I'm making is that TDP is pretty useless gauge of power consumption.