[HN Gopher] AMD Unveils Ryzen Mobile 7040U Series with Zen 4c Ef...
___________________________________________________________________
AMD Unveils Ryzen Mobile 7040U Series with Zen 4c Efficiency Cores
Author : cebert
Score : 70 points
Date : 2023-11-03 10:52 UTC (12 hours ago)
(HTM) web link (www.anandtech.com)
(TXT) w3m dump (www.anandtech.com)
| neogodless wrote:
| Definitely curious how this plays out:
|
| > Unfortunately, however, because Windows sees all of the cores
| as identical, it also has no proper insight into energy
| efficiency here. Specifically, Windows has no idea that the Zen
| 4c cores are meant to be more energy efficient, so it will be
| making scheduling decisions based solely on workload/frequency
| metrics. This means that AMD is not able to take full advantage
| of the energy efficiency advantages offered by the Zen 4c CPU
| cores, as Windows isn't able to explicitly schedule threads on
| the more efficient cores. (An issue Intel gets around with their
| more meddlesome Thread Director)
|
| Given that they are on feature parity with Zen 4, but trade
| higher clock speeds for density and efficiency - will we _see_
| the efficiency if Windows doesn 't know any better?
|
| Would Linux be able to do any better if it can tell the cores
| apart?
| tremon wrote:
| Yes, Linux is aware of asymmetric cores and can schedule more
| efficiently. big.LITTLE core architectures are more common in
| ARM systems, so Linux developed that support over ten years
| ago: https://lwn.net/Articles/501501/
|
| The official documentation is at
| https://www.kernel.org/doc/html/latest/scheduler/sched-energ...
| . I don't know if the kernel already has an energy model that
| can apply to the Zen4/Zen4c cores, probably the
| model/instrumention must be explicitly added.
| Aardwolf wrote:
| How is Linux aware of this, are there CPU id instructions to
| differentiate the Zen4 from the Zen4c cores?
|
| If yes, is there any reason Windows can't receive a patch to
| be able to do so?
| smoldesu wrote:
| I am not an expert, but I believe it still requires some
| manufacturer effort on Linux. I bought an Alder Lake system
| pretty close to launch, and I had to wait a few months for
| kernel-side Thread Director[0] to fix asymmetric
| scheduling. Performance was really janky before that
| update, even though the power consumption and iGPU seemed
| fine. Nowadays things are fine, though I'm not sure how
| much of the asymmetric support was already in the kernel.
|
| > is there any reason Windows can't receive a patch to be
| able to do so?
|
| Probably not, given that Thread Director also runs on
| Windows AFAIK. AMD could probably cook up a solution if
| they needed one, but their E cores look pretty powerful
| from the get-go. My guess is that it won't need such a huge
| patch to perform well.
|
| [0] https://www.tomshardware.com/news/intel-thread-
| director-comi...
| adam_arthur wrote:
| This doesn't seem correct?
|
| "Windows 11 boosts performance of big.little x86 CPUs shows
| testing"
|
| https://www.neowin.net/news/windows-11-boosts-performance-of...
|
| "Microsoft and Intel confirm Windows 11 is optimized for
| Big.Little design"
|
| https://www.neowin.net/news/microsoft-and-intel-confirm-wind...
| Dalewyn wrote:
| Windows 11 knows how to use Intel performance and efficiency
| cores thanks to Intel providing Intel Thread Director which
| gives some hints to Windows 11's scheduler.
|
| AMD, from what I can tell, doesn't provide an equivalent to
| Intel Thread Director so Windows 11's scheduler has to work
| blind not unlike Windows 10's scheduler when working with
| Intel performance and efficiency cores.
|
| So all else being equal, it's reasonable to assume Windows 11
| will not take full advantage of AMD's performance and
| efficiency core architecture because the scheduler is working
| blind.
| The_Colonel wrote:
| > AMD, from what I can tell, doesn't provide an equivalent
| to Intel Thread Director
|
| Isn't that simply because AMD so far didn't have any
| heterogenous cores and they will quite possibly/likely work
| with Windows to add support for them (just like Intel did)?
| It might take some time, but it seems needlessly
| pessimistic to expect that this won't happen in some form.
| Sakos wrote:
| But why should it be on AMD? This needs to be a part of
| the OS as it is like in Linux, or as a user you're
| penalized for picking the company with less solid
| connections to Microsoft and less budget available to do
| something like Intel's thread director (which is how
| Intel's mixed cores are "supported" by Windows). Windows
| doesn't have any native support for heterogenous cores.
| It just takes the CPU's advice on what to do. That seems
| crazy to me.
| The_Colonel wrote:
| Well, who adds support for this into the Linux kernel?
| It's also the CPU vendors.
|
| While there is certainly a need for some common scheduler
| logic, there also needs to be per-vendor or even per-
| model support added, since the OS first needs to even
| figure out which cores are which and each vendor's
| efficiency cores have different characteristics.
| Sakos wrote:
| AMD can't do that for Windows. Why do they have to add a
| hardware component to their CPU's to do it like Intel can
| afford to?
|
| > Intel's Thread Director controller puts an embedded
| microcontroller inside the processor such that it can
| monitor what each thread is doing and what it needs out
| of its performance metrics.
|
| Linux literally has native support for heterogenous cores
| that works for both AMD and Intel. There's a world of
| difference between contributing to the kernel to ensure
| their CPU's work well and AMD being forced to put a
| microcontroller in their CPU and develop their own CPU-
| internal scheduling system.
| rewmie wrote:
| > But why should it be on AMD?
|
| It's in the best interests of OS vendors to get
| processors to work.
|
| It's in the best interests of CPU vendors to get
| processors to work optimally on major platforms.
|
| AMD's business is selling processors. Customers buy them
| if they perform better than the competitor's offers at
| the same price range. If your competitors optimizes
| implementations but you drop the ball and go with
| unoptimized ones, it matters nothing if your product
| performs better in theory if customers don't see that in
| the real world.
| pedrocr wrote:
| AMD has had heterogeneous cores since at least the
| beginning of the year with the 7900X3D and 7950X3D. The
| differences between cores there are even bigger than with
| these parts. Some cores clock lower but have more cache
| than others so depending on workload the optimal cores
| are different. With Zen4 vs Zen4c apparently only the
| clocks change so some cores are strictly better than the
| others.
| The_Colonel wrote:
| Yes, that's true, AMD actually had such models since the
| 5X00 series. As I understand these models are somewhat
| niche and focused on the gaming market where AMD has some
| custom support for selecting the 3D cache cores.
|
| Having said that, I don't really want to defend MS, they
| should add full support for this, but basically I believe
| it's just a matter of time.
| pedrocr wrote:
| The 5800X3D had all cores with extra cache just like the
| 7800X3D. They didn't do a 5900X3D or 5950X3D so the
| problem didn't exist before.
| Sakos wrote:
| Windows 11's "support" is more of a lazy hack. It doesn't
| work without the CPU literally telling it how to schedule
| threads across its cores:
| https://www.anandtech.com/show/16881/a-deep-dive-into-
| intels...
| Sakos wrote:
| I'm surprised that after 3 years since Intel's first big/little
| CPU (Lakefield), Windows still doesn't really support mixed
| cores. And that's over 10 years after the first ARM CPU with
| that kind of configuration. With their repeated attempts to get
| into the mobile space, you'd think they would've put more of an
| effort into this.
| torginus wrote:
| That simply seems untrue. Heterogeneous cores have existed
| since forever. SMT-aware has been a CPU feature in Windows for
| close to 2 decades, not to mention support for Intel's big-
| little designs
| tedunangst wrote:
| How much does it matter? The lines in the graph are pretty
| close together, and I'm assuming they picked an example that
| accentuates the difference.
| fredgrott wrote:
| What is in the article is that AMD has or is deploying Phoenix 2
| to budget laptops while Phoenix 1 chips with AMD's AI chip is the
| higher end laptops.
|
| It's AMD shot over the Apple line-up of laptops all at over 5
| GHZ!
| Symmetry wrote:
| AMD's efficiency cores are much more similar to their mainline
| cores than for either Intel or ARM. Zen 4c cores have the exact
| same pattern of transistor connections as a regular Zen 4 core,
| it's just that the transistors much more of a consistently low
| width and so laid out differently, with those transistors that
| have to push signals long distances or to many consumers not
| allowed to grow as much. This means you can't drive the clock
| rates as high, but at the benefit of a smaller core and generally
| lower power usage.
| rewmie wrote:
| > AMD's efficiency cores are much more similar to their
| mainline cores than for either Intel or ARM.
|
| I apologize for going off on a tangent, but now that we have
| the benefit of hindsight what was the verdict on AMD's
| Bulldozer microarchitecture?
|
| I recall that Intel invested a great deal on its anti-Bulldozer
| smear campaign with their "no true cores" accusations, but
| nowadays it seems that cheaper non-performance many-cores are
| the winning recipe.
|
| https://en.wikipedia.org/wiki/Bulldozer_(microarchitecture)
___________________________________________________________________
(page generated 2023-11-03 23:02 UTC)