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Comment by Scoundreller | Hacker News Reader

Interesting non-BIOS observations:

> So I popped everything together, made sure it benchmarked as expected, tested an Intel Arc A750 in preparation for testing on a Raspberry Pi, and then decided the 7900x's egregious power consumption wasn't to my liking the thing idled over 90W, and would eat up over 285W while compiling Linux!

> I wanted to enable AMD's 'Eco' mode, which limits the TDP from the stock 170W to either 105W or 65W. And in my own benchmarking (which happened later on, but I'm including the data here because it's kinda insane), the CPU got about 96% of its 170W performance when I limited it to 105W. And at that level, it idled at 45W and maxed out at 206W. Much better.

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Yes, we're unfortunately back to an unhinged race for the performance crown at any cost.

When were we not in an unhinged race? GHz sells chips, gotta get as many as possible; it's just AMD and Intel have gotten really good at pumping the watts through the chips lately.

But you can buy CPUs with lower power limits, sometimes these are released later in the cycle though, or set the limits yourself. Or probably just leave it at defaults and not usually get up to the crazy high numbers anyway; most desktop use cases aren't going to scale usage so high, although there's plenty of examples that do.

Before Ryzen AMD was way behind for many years and Intel didn't have to compete. TDP was lower for a long time. The previous big run achieving speed by pushing power was in the Pentium 4 era if I remember correctly.

Yeah I was going to say, this reminds me of the Pentium 4 days when Intel ran into problems with both maxing out the clock speed and their huge instruction pipeline. I just want a machine that can perform well under pressure, but doesn't double as a space heater while idle...

Higher idle power consumption is more common on AMD CPUs (I think it's inherent to their design). I don't think intel CPUs consume nearly as much power when idle. Oddly enough, AMD GPUs also have the same problem under certain conditions (multiple monitors, or high refresh rates can result in 100w idle GPU power )

But I agree that the power consumption figures under load are a bit nuts, and intel/amd now seem to be eager to double max power use if it means they can squeeze 5% more performance out of the die.

> Higher idle power consumption is more common on ...

On that note, the new-ish ATX12VO standard Intel has been pushing apparently allows for motherboards with much lower idle power consumption:

https://en.wikipedia.org/wiki/ATX#ATX12VO

https://hackaday.com/2021/06/07/intels-atx12vo-standard-a-st...

Sounds like a win if it becomes reasonably widely used.

They're very close actually, at least at stock frequency.

https://www.guru3d.com/articles_pages/amd_ryzen_9_7900_proce...

Both Intel 12900k and AMD 7900 are 78W idle.

So it's basically neck-and-neck on idle power because those CPUs are around the same performance.

Where the power usage is crazy different is multicore load, 320W for the Intel vs 158W for AMD.

edit: actually an AMD 7900X is 299W on MC load. A 7900X is 15% faster on MC than a 7900. So Intel and AMD seem quite similar on power usage.

Anecdote:

With me using my computer, 2 x 27" QHD 144Hz monitors, my AMD GPU is using 28W, while the CPU is using 18W.

(Radeon RX 6700XT 12GB, Ryzen 9 5900X 12-core)

I know the Zen 4 / Ryzen 7000X use a lot more power, as they are designed to pull power and use all available thermal headroom all day!

A 6700xt should idle at 6-7w with only one monitor. If it idles at 28w it means there is something it doesn't like about your monitors that forces it to keep the memory clocks at max. Try setting them at the same resolution, refresh rate, and depth/bpc).

The monitors are nearly identical (slightly different Acer models) but the settings are identical (same resolution, refresh rate, depth/bpc.)

VRAM clocks are 1990Mhz.

I had a similar situation with two identical monitors except for some reason one of them was a slightly newer revision (same model!) and had an EDID that made it look as an 10bpc panel instead of 8bpc like the older revision. Setting both to 8bpc reduced the idle power consumption by 4x. If you are on windows, you may need some additional tool to be able to change the bpc (the AMD control panel applet works too).

Which number are you looking at? 18 W idle for a 5900X is very low. 30-40 W is typical for these. Your system is probably not configured correctly, is using slow RAM or you're looking at something other than package power.

GPU idle power seems quite high though, but as I understand most AMD GPUs struggle with power management with more than one monitor connected (no experience here, last AMD GPU was 2012).

If you mean PPT then yes, that's closer to 40W.

CPU Power is 15-20W. SOC Power shows 17W.

The RAM is DDR4-3600 CAS16 running at 1800Mhz, which I don't believe is slow.

GPU is "relatively" idly but just having Ryzen Master or Adrenaline open and displaying these values means it is not truly idle.

18w idle is rather normal for what the ryzenmaster monitoring software will report (which I believe is PPT) . On Intel for PPT you will usually measure 0-5W -- AMD idle power consumption is really bad on desktops.

I’m not sure why I’d care. An extra 100w amounts to a couple cents an hour for most people. Not relevant most of the time, and will shave time off almost any CPU task (as this is increasing the single-threaded speed, which applies to almost everything - sans memory or storage bottlenecks).

Sounds like a worthwhile trade off for most people to me, and more so if you do anything remotely CPU-intensive.

Sure, if you enjoy running a space heater in the summer that doubles as a jet engine regarding the sound scape for 4% more performance then more power to you. ;-)

This is of course, hyperbole. And geez, don't place your PC case with the vents blowing at you. Even at 100% CPU, noise should not be noticeably different if you’re using anything besides the stock cooler. Stock coolers are of course notorious for being bargain-basement tier in noise/performance.

He may just have a well binned chip, they have to configure for the lowest performing chip otherwise yields would be down and prices would be through the roof.

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