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Comment by formerly_proven | Hacker News Reader

Both X (AMD) and K (Intel) lean heavily towards "gib last 5 % perf" in order to win benchmarks in reviews across their line-ups. The non-K 13th gen SKUs aren't out yet, but in the largely similar 12th gen they also enjoyed substantially lower power consumption.

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According to https://www.anandtech.com/show/17641/lighter-touch-cpu-power... Intel is much more power sensitive than AMD is. In other words, limiting Intel power consumption will hurt performance a lot more than limiting AMD power consumption does.

I'm using a 5950X, and in the BIOS there is a setting where you can enter the power limit in Watts. So while the "X" CPUs consume more power as configured out-of-the-box, you can still set your own limit as desired.

I have a 3200G and I limit it to 35W(of 3 built-in values, 64, 45 and 35) since I run it off a picoPSU. Haven't done much testing without the power limits, but it's plenty peppy at 35W.

These lower power limits reduce performance a lot on chiplet CPUs (unlike your monolithic APU). The impact is maybe a little less crass on Zen 4 because the 7nm IOD seems to use less power than the old 12nm one used in Zen 2/3.

For example, a 5600X in CB R20

   PPT   Freq      Points (nT)  Core power
   82 W  4500 MHz  4350         54 W         (stock)
   65 W  4200 MHz  4000         43 W
   38 W  2500 MHz  2400         17 W         (lowest allowed)

The SoC/uncore consumes around 15-20 W on Zen 2/3, so at 38 W you only leave 15-20 W for the actual CPU part of the CPU. Meanwhile the low-load and idle savings are essentially nil because all of the idle power is the IOD/uncore.

I just read someone posting in the Intel subreddit who was concerned about the temps he was seeing on his 13900k that was being overclocked and was hitting 100C on an All In One Water cooler. Someone chimed in for the amount of power it was consuming (350+ watts) that it was normal. Yikes. All that power for a few extra FPS.

Good example of "input=voltage^2*quantity*size; output=voltage*quantity*size" as the napkin math of transistor processors.

Unless you are using a laptop (as these processors aren't mean for) or are running a datacenter (which these processors aren't meant for) does anyone really care about 65 vs 150w differences?

Yes, to avoid getting a space heater when you turn on your computer during the summer. In winter it's not really that bad, as you get both compute and heating from the same device.

Lower power bills help too. And let's not forget the ridiculous power numbers that new GPUs are consuming.

if only 100W would produce any meaningful amount of heat, that would be wonderful. A simple space heater runs at 1500W and can only barely help heat a medium sized room as supplemental heat. Unfortunately (for heat purposes), computers waste a bunch of that electricity on actually doing computations.

The electricity spent doing computations is still turned into heat.

High-end GPUs have been around 250-300 W for a very long time (with the odd xx95 X2 Ultra Titan model consuming more). "Ridiculous power numbers of new GPUs" is a pure-bred meme.

GTX 1080 was 180W. I think everyone agree that 1080 was high-end at that time. What's happening now is that xx80 series now become ultra-high-end silently, as we can also see price rising.

Even if power consumption is not a concern, there's a need to account for power dissipation. Using 65W allows for a low-noise air cooler or a nearly-silent AIO, and it also allows for smaller form factors with compromised cooling solutions.

Actually 65W allows for fully passive cooling solutions. See e.g. https://streacom.com/products/fc8-fanless-mini-itx-case/

I personally do not care that much about peak power, if I am actually crunching numbers I might as well do it as fast as possible.

However I care a lot about idle power consumption, with a desktop computer turned on most of the day, these small inefficiencies really add up.

As a concrete example, my desktop GPU has a well known bug that makes it consume 30 W more idle than it should. For an always on desktop, that's 260 KWh wasted per year.

in europe that's easily 130 euro nowadays, crazy

I am running my 7950X at 105W, because I get 97%-99% of the performance on my own workloads and extremely quiet operation. At 65W I'd lose too much performance and wouldn't gain anything meaningful; at 170W the PC would be audible.

As others have said, there are dissipation considerations in a desktop, too. I would absolutely hate having to work next to a jet-engine or having a fridge-sized rig to fit some absurd cooler. Others don't care as much. My 135W-rated Xeon does get audibly loud despite the big-ass Noctua, especially when the GPU next to it is also working hard. If it wasn't during gaming, when I can't hear it, I would hate it.

But I also think the actual usage profile should be considered. Typically, my CPU waits around doing nothing. Occasionally, I ask it to build whatever project I'm working on. I can tolerate some noise during this time if it's not too long, and if it noticeably shortens the time I have to wait for it. So if the idle consumption is similar, but it can get very fast when needed, I'm all for it.

> I would absolutely hate having to work next to a jet-engine or having a fridge-sized rig to fit some absurd cooler.

Even SFF cases can fit 240mm or 280mm AIOs these days.

Old standby heat sinks like the Noctua NH-D15 can cool 200-300W CPUs quietly, and they fit in common cases. They have a 120mm tall version for slightly smaller cases that doesn’t give up much in benchmarks.

I think the cooling challenges have been overblown, honestly. It’s kind of trivial to quietly cool powerful CPUs these days.

> My 135W-rated Xeon does get audibly loud despite the big-ass Noctua,

Unless there’s something wrong with airflow or your mounting, your fan curves are almost certainly too aggressive.

A lot of motherboards, especially workstation and server boards, will ramp fans to 100% by default. You probably don’t need that. Adjust the curves until it’s quiet, don’t worry about getting the absolute lowest possible temperatures. This is what OEMs do. If you build your own, you’re expected to do it yourself.

The NH-D15 is what I actually have, and all other fans are Noctua save the GPU which has whatever the manufacturer figured was good enough. Now the PC isn't outrageously loud, but the fan hum can become tiring after a while if the CPU is busy. It's almost inaudible when idle.

Maybe there's an issue with general airflow in my case (an older Fractal Design Define R something).

Important for small form factor PCs, which are basically ITX PCs in the smallest possible case, often below 10L in size.

In my experience computers last longer when cool, and even more important is a minimum number of heat cycles. Things like capacitors on motherboards use chemicals that break down over time, and more quickly if they are hotter. Sure you can buy capacitors that will last 10 years in challenging conditions, but I doubt any consumer motherboards do.

Ideally my desktop lasts 10 years, even if it ends up in some kind of secondary usage scenario. To that end I want it silent, well cooled, and to experience minimum temperature swings.

I usually end up with 2x 140mm intake fans, a 120mm fan on top of the CPU, and one of the decent PSUs that go to zero RPM when at low loads. In a case like this a 65w TDP CPU (that's normally going to idle at way less) is MUCH easier to cool than a 150w-300w (the common range for the alder lake Intel chips). No exotic cooling (water, water blocks, piping, reservoir, pump, etc) needed, and not a big deal if the bearings loose some lubrication or dust accumulates on a filter.

Sure would some CPU intensive workloads go 10-20% faster at 2x-3x the power? Sure. Do I care, no. I'd rather spend the extra purchase price, cost of electricity, cost of cooling, and related on ECC memory. I don't really want to be able to hear when my desktop is busy, should be silent all the time.

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