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paulca:
A thought provoking thing is that pulling 320W at 900mV is about 350Amps.  The CPU is 140A EDC on the dies and 160A total.  The motherboard can supply it with 200A.

But that GPU figure of 350 Amps is insane.  I've not seen a pin map of it, but I'm going to go out on a limb and suggest that as much as 50% of them are going to be 1.5V rail and ground.  There is no way they are push 350Amps through a bit of silicon on 7nm process.  I expect that power enters the die in a widely parallel fashion spread out across the whole die and isn't "transported" around the chip unless absolutely necessary, so each little 5mm square area is only pulling a few amps locally and only a few dozen amps on the nearest Vcore pin.

What do you think?

I know power is generated from multiphased VRMs, so each VRM is only generating a burst of high current on a duty cycle.  I assume again that those VRMs output along many parallel tracks which cover the shortest possible distance to a Vcore pin.

Of course the main issue with amps is heat.  But given these things have coolers capable of handling 500+W, certainly for the die and VRMs, there should be little concern of it melting.

The mobo has (IIRC) 12+4 VRM phases, which I believe is 12 CPU Core VRMs and 4 for the rest.  I didn't count the GPU VRMs when I had it apart, but there are two solid lines of Vcore VRMs either side of the chip socket.  The modded cooler has heat transfer pads for both rows, front and back side of the board, in addition to the VRAM modules and of course the GPU die.  It must be 8 each side?  10 each side?
Howardlong:

--- Quote from: paulca on April 20, 2022, 08:36:17 am ---I spent 2 hours trying to over clock the 3080 GPU.  I could get a little here and there, but nothing substantial.


--- End quote ---

The overclocking thing is a sure fire way to lose much of your life!

I had a reasonable uptick in Ethereum hashrate on my 3090 using a static config, but it's a completely different config on the card for gaming, where I used a voltage/frequency curve.

Overclocking the 5950x took several weeks elapsed delving into the per core curve optimiser to get it 100% stable, tweaking each core until none crashed anymore.

I'm still not really sure I've ever benefitted that much from the tweaking.
Ranayna:
Modern hardware, both CPUs and GPUs, are already near their limits.
These beasts gobble up power like no tomorrow, for at best marginal performance increases while gaming.

You should look at undervolting to reduce power consumption for little to no actual performance loss, outside of artificial benchmarks.
Some cards can actually increase in performance when undervolted.
Or even actual underclocking, to further reduce power consumption with a little more performance loss, depending on the workload.

hans:
Exactly. On my server I run a 5600G processor. In the interest of efficiency (it's a server - not a desktop), I've chosen to reduce the package power to 35W. These CPU dies are derivatives of their mobile SOCs, so the BIOS may support multiple TDP profiles. In my testing it yielded only 10-15% lower Cinebench scores, but *halved* power consumption (went from 130W system load to about 60-65W, around 12W idle). Since my server will transcode the odd movie for storage, this significantly cuts back on the energy cost for that job.

In my desktop I run a 3900X, and never gained anything by tweaking the settings. Out of the box it boosts 4GHz+ all core at around 80-85C under a big tower cooler. I've tried a slight undervolt, enabling PBO, etc. but I was not very impressed by what any of these did. Either the CPU became unstable for the same performance, or ran extremely hot (90C+ with PBO) for a 0.5% performance bump.

And I haven't even looked at the 3080 card I've got. The release with unstable BIOS's from some manufacturers (and the red herring that looked at a bunch of capacitors) didn't warrant me investigating any further.
paulca:
It amusing how many people don't "like" PBO. Some people say it idles at 1.5V which they don't like so they don't use it.  Others say it runs the system hotter than it should.  Both non-sense according to AMD, the chips are fine to 105 and will shutdown at 95-100 anyway.  Also  reading into PBO it is a complicated beast doing a lot more than most overclockers can, but doing it 100 times a second.  I mean at very least there will be times when a core won't got to 4.xGhz and a static overclock will become unstable.  A PBO one won't, because PBO will know to back off a bit.

The thing about PBO is, it will save you power, it turns core OFF when it needs to.  It undervolts and underclocks them when they are no being used much.  The 3400X will boost higher than 4Ghz.  It's clock boost is 4.3Ghz and it will go higher than that.

The other thing about PBO is that motherboard manufacturers often ship with "their" tweaked/optimized versions of the control parameters, which may not be ideal or may be too unstable.
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