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Comment by perihelions | Hacker News Reader

AnandTech sees some intriguing regressions on certain benchmarks,

https://www.anandtech.com/show/18747/the-amd-ryzen-9-7950x3d... ("CPU Benchmark Performance: Simulation")

Worst is Factorio, which is down -47% against the 5800X3D (a previous-generation CPU that also uses stacked L3 cache), on the benchmark "10K trains". Wonder what's going on there?

- "We would have expected higher performance in our Factorio benchmark, as the Ryzen 7 5800X3D and its 3D V-Cache did yield some impressive gains. This is likely due to the AMD PPM Provisioning and 3D V-Cache driver opting for frequency over cache when running this benchmark."

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When they manually forced it onto the CCD with 3D-Vcache, they saw a 100% speedup:

"As we can see in our Factorio benchmark, we saw massive gains of over 100% when forcing the Ryzen 9 7950X3D to use the CCD with the 3D V-Cache as opposed to letting AMD's PPM Provisioning and 3D V-Cache Optimizer drivers do their thing automatically."

Oh good catch! I didn't read that far. It's on page 11:

https://www.anandtech.com/show/18747/the-amd-ryzen-9-7950x3d... ("Conclusion")

5800x3D has a single CCD so no need to choose which CCD to use.

The interesting one will be the 7800X3D.

So presumably a bug that can be fixed by either AMD updating their optimizer, Factorio updating to work better with it, or both?

If it's a problem for Factorio it's also a problem for others, so definitely something to fix on the AMD side.

Its more of a fundamental scheduling issue. The unlike big/little cores OS has no idea what apps "prefer" cache or frequency.

An OS can easily run an app on each for a few milliseconds, look at the performance counters to see which ends up with more instructions executed, and then move the task to where it performs best.

From time to time, it can retry the test, because software frequently changes what it spends time doing.

But apps like factorio are extremely dynamic, so thats either going to be flakey or its going to spend a lot of time/energy bouncing the process between cores.

I wouldn't be too worried about this personally, as configuring the few really sensitive apps with ProcessLasso or Aniancy is pretty easy.

I feel that with good statistics this could be done in the OS scheduler successfully. But it’s not my area of expertise.

I don't think the average Factorio gamer is going to know that they should do this or how. They will just know that their new CPU which was supposed to have better gaming performance is doing very, very poorly.

You are talking about Factorio players who specifically bought an 3D-L3 CPU, I would guess awareness would pretty high, personally...

> You are talking about Factorio players who specifically bought an 3D-L3 CPU

Factorio players don't necessarily know anything about computers. And you don't know if they bought this CPU or if it came with their fancy prebuilt.

I'm pretty sure this is how Nvidia's game ready drivers work. They come with a bunch of pre-made profiles for popular video games, so the optimal settings are configured based on what applications are being executed, which is also why you have to let it scan for your games, so it knows what executables to watch for, so it can properly select the right profile to use.

And that's why we have the "Game Ready" driver mess.

My understanding is there's a certain amount of nvidia cleaning up after the game developers too. e.g. replacing poor performing shaders with optimised versions or just old-MS style "let's change how the driver works to keep the game working". Which is why they've been so resistant to opening the driver, they believe some of their perf advantage/secret sauce is in the driver rather than the hardware.

Affinity in the O/S?

A properties page for the executable with a checkbox for “favour stacked cache cores” or some such.

Factorio is infamous for being radically memory bandwidth limited. Which yes is a problem others will have... but not many in gaming afaik.

Given the primary selling point of these CPUs vs their non-X3D version is having more cache for memory access heavy workloads, if this is not a problem for your workload you're likely not in a position to gain much from the X3D variant anyway.

Or just buy the X3D that have cache on each CCD instead of half of them.

More precisely, buy the X3D that has only one CCD.

There is currently no consumer model with 2 CCDs and X3D on both of them.

Right, so the 7800X3D (due in April), the old 5800X3D, or any future threadripper or Epycs with the X3D.

Best L3 per core outside of the X3Ds it the 7600 or or 7900 CPUs that come with the full size L3 (32mb PER ccd) but only 6 cores per CCD (instead of 8).

Can't you disable the CCD without the 3D cache? I remember being able to disable 3 CCDs on my Threadripper using Ryzen Master for gaming.

Yeah... if you're going to see bigger gains from the cache, fewer cores in 7800X3D in early April is probably a better option (same for gamers).

I saw on Hardware Unboxed that the non-X3D cores were being used for Factorio and that reviewer manually disabled it to test correctly.

Depends on good scheduling choices since some threads benefit from the higher clocked CCD and others benefit from the higher cache CCD. Sounds like AMD is using a lookup table style scheduler on windows. I believe the system mostly schedules the higher clock CCD by default.

Similar problem to big.little but less differentiation between the cores. It's big.big. Kind of a mess outside of the primary use case that is games on windows with a static tuned scheduler.

Its worth say that the 3D V-Cache is only on the left of the two dies, while the other is frequency unlocked.

Also linking my favorite tech reviewers benchmark they do some great Linux/tech videos also! https://www.youtube.com/watch?v=jNMcdIkef_c

Linux video here: https://www.youtube.com/watch?v=5yDsEbSxHkM

I didn't read the article but according to Gamers Nexus latest video you REALLY need the latest BIOS and Chipset drivers for this part because it is what tells Windows which CCD the game threads should be parked on.

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