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Intel completely disables AVX-512 on Alder Lake after all

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Re: Intel completely disables AVX-512 on Alder Lake after all

#141

Post by CodesInChaos »

nullifidian wrote: post #94
qayxc wrote: post #18

Much ado about nothing, IMHO. AVX-512 isn't advertised by Intel as a 12th gen desktop CPU feature and doesn't provide any advantages for most desktop users anyway. Sure, there's niche applications like some particular PS3 emulator, but I don't share the author's opinion w.r.t. to performance and efficiency in desktop use.

It doesn't provide any advantages because there is no install base, so desktop software doesn't utilize it. It's just a wider SIMD instruction set, and I'm confused why people relegate it to HPC only category.

AFAIK it downclocks the CPU, even if the AVX512 instructions are only a tiny fraction of instructions. So you only benefit from AVX512 if you use it enough. While 128 bit SIMD give you a speedup if you use it for a few functions that need it, without slowing down the rest of your code or even unrelated applications.

Re: Intel completely disables AVX-512 on Alder Lake after all

#142

Post by MikeKusold »

tymscar wrote: post #122
Fnoord wrote: post #20

Earlier quoted context omitted.

Nvidia do the same with disabling passthrough on consumer GPUs (gotta upsell Quatro). However I would say avoiding Intel completely is unnecessary. They're a good FOSS citizen when it boils to things like WLAN and GPU. Its just that with AMD, you can hardly go wrong on CPU and GPU side. Especially on Linux.

Not anymore! Nvidia gpus can be passed through just fine with no fixes. I use mine like that daily

Are you doing a full pass through or vGPU?

Re: Intel completely disables AVX-512 on Alder Lake after all

#143

Post by rasz »

Fnoord wrote: post #20
SkeuomorphicBee wrote: post #10

Stuff like this is why I plan to never buy Intel ever again. I always disliked Intel's strategy for market segmentation by disabling specific instructions, I much prefer AMD's strategy of segmenting just by speed and number of cores. It is really annoying that with Intel you can't run the same program on the server and on your desktop, it makes development and testing a huge pain.

Nvidia do the same with disabling passthrough on consumer GPUs (gotta upsell Quatro). However I would say avoiding Intel completely is unnecessary. They're a good FOSS citizen when it boils to things like WLAN and GPU. Its just that with AMD, you can hardly go wrong on CPU and GPU side. Especially on Linux.

>Its just that with AMD

- forbidding motherboard manufacturers to implement backward compatibility

- PCIE 4 and 'PCI Express Resizable BAR' CPU features linked to the price of northbridge

Re: Intel completely disables AVX-512 on Alder Lake after all

#144

Post by qayxc »

josephcsible wrote: post #136
qayxc wrote: post #18

Much ado about nothing, IMHO. AVX-512 isn't advertised by Intel as a 12th gen desktop CPU feature and doesn't provide any advantages for most desktop users anyway. Sure, there's niche applications like some particular PS3 emulator, but I don't share the author's opinion w.r.t. to performance and efficiency in desktop use.

I wouldn't say that Intel taking away a working, if niche, feature from their hardware retroactively after users bought it is "nothing".

It worked for one SKU at launch and by disabling up to 50% of the cores of the others. Calling that a working feature is a bit of a stretch already.

Re: Intel completely disables AVX-512 on Alder Lake after all

#145

Post by nullifidian »

CodesInChaos wrote: post #141
nullifidian wrote: post #94

Earlier quoted context omitted.

It doesn't provide any advantages because there is no install base, so desktop software doesn't utilize it. It's just a wider SIMD instruction set, and I'm confused why people relegate it to HPC only category.

AFAIK it downclocks the CPU, even if the AVX512 instructions are only a tiny fraction of instructions. So you only benefit from AVX512 if you use it enough. While 128 bit SIMD give you a speedup if you use it for a few functions that need it, without slowing down the rest of your code or even unrelated applications.

In heavily vectorized applications you still get a sizable speed up over AVX2, e.g. in tasks like video encoding. In mixed/real-time applications this issue could be solved by dedicating/pinning a thread with the AVX-512 payload to a core, automatically or manually. Not sure if such policies have been implemented in practice.

Re: Intel completely disables AVX-512 on Alder Lake after all

#146

Post by rasz »

PragmaticPulp wrote: post #67
marcan_42 wrote: post #38

Earlier quoted context omitted.

Don't forget it's not just instruction sets; Intel is the reason we don't have ECC RAM on desktops. Every other high density storage technology has used error correction for a decade or two, but we're still sitting here pretending we can have 512 billion bits of perfect memory sitting around that will never go wrong, because Intel fuse it off on desktop chips. I guess only servers need to be reliable. AMD supports EC…

> Intel is the reason we don't have ECC RAM on desktops. Intel has offered ECC support in a lot of their low-end i3 parts for a long time. They’re popular for budget server builds for this reason. The real reason people don’t use ECC is because they don’t like paying extra for consumer builds. That’s all. ECC requires more chips, more traces, and more expense. Consumers can’t tell if there’s a benefit, so they skip i…

>You’re blaming Intel’s CPU lineup for people not using ECC RAM on their AMD builds?

Yes. ECC was standard on first IBM PC 5150, on PS/2 line, on pretty much all 286 clones etc. Intel killed ECC on the desktop when moving to Pentium, prior to that all of their chipset products (486) supported it. 1995 artificial market segmentation shenanigans https://www.pctechguide.com/chipsets/intels-triton-chipsets-...

Re: Intel completely disables AVX-512 on Alder Lake after all

#147

Post by vardump »

formerly_proven wrote: post #73
codeflo wrote: post #11

If all of this was planned (and I’m not saying it is), that would have been very clever. It would work like this: 1. You “accidentally forget” to disable the feature in hardware. Given how competitive the market is, motherboard manufacturers can be relied upon to enable it in their “1337 OVERCLOCKZ” mode. No conspiracy is needed. 2. You “tolerate” this practice just long enough to win the critical initial wave of rev…

I've voiced this before but I think AVX-512 is completely irrelevant in the consumer space (which imho makes titles like "Intel artificially slows 12th gen down" incredulous). Even for commercial applications - sure there are some things that benefit from it. On the other hand, I work in HPC and even in (commercial, not nuke simulations or whatever the nuke powers do with their supercomputers) HPC applications AVX-51…

I could absolutely make a good use of AVX-512 for a lot of applications, including consumer space. It's even better than AVX2 when it comes to flexibility, and of course, it's double width.

Of course because of lower clock speed and the associated penalties limit it a bit. But you can work around those limitations, for example perhaps by dynamically switching between AVX2 and AVX-512 paths depending on workload.

Re: Intel completely disables AVX-512 on Alder Lake after all

#148

Post by Someone »

jacquesm wrote: post #27
gambiting wrote: post #17

Earlier quoted context omitted.

Bringing a product in line with specification is very much fixing it. Even if the fix happens to be disabling something.

Yes, but once it has shipped and people may have come to depend on it it will break stuff, not fix stuff. Besides the obvious benefit of first having benchmarks out there claiming these chips are better than they really are. So this change just benefits Intel, and nobody else. If it would be a fix then it would be that something that was advertised did not work, and now it does.

> Yes, but once it has shipped and people may have come to depend on it it will break stuff, not fix stuff.

That may apply to every change, including things everybody agrees on to be bug fixes. If, for example, you improve the number of correctly returned bits for computing sin, that can break programs, for example games that want to keep world models in exact sync across systems.

From what I read here, intel didn’t advertise this feature and it wasn’t easily discovered. If so, I don’t think customers have any claim against Intel for the CPUs.

_If_ motherboard vendors advertised/promoted it (could be as simple as blogging about it), I would think people who bought a motherboard because it allows activating this feature will have a case against them (in the EU and possibly elsewhere, the seller is responsible for the product being fit for purpose, not the manufacturer, so it would be the seller, but let’s ignore that)

Legally, there also is the issue who applies that update. From what I read, that’s the motherboard. Here again, I would say that, if customers have a case, it would be against whomever sold them the motherboard (e.g. if that silently applies the update) I don’t see any indication that Intel, as a CPU manufacturer, forces existing customers to install this.

Re: Intel completely disables AVX-512 on Alder Lake after all

#149

Post by tmccrary55 »

amluto wrote: post #135
hajile wrote: post #118

Earlier quoted context omitted.

> The AVX-512 instructions not only weren’t enabled by default, they couldn’t be enabled at all unless you went out of your way to disable the efficiency cores completely. They also wouldn’t benefit your workload unless disabling those extra cores was offset by the AVX-512 instructions on the remaining cores. If your code benefits from AVX-512, it'll probably benefit from turning off the efficiency cores too. Sixteen…

> The real solution would be for Intel to detect the presence of AVX-512 instructions then automatically and unconditionally pin the thread to the big cores. It wouldn't be hard either, just catch the unknown instruction exception and see if it is AVX-512 then move the thread. Having actually worked on this, it’s quite a bit more complicated, although it is possible. For better or for worse, though, Intel made a deci…

Boost your benchmarks with AVX-512 by subscribing to Intel+

Re: Intel completely disables AVX-512 on Alder Lake after all

#150

Post by duxup »

im3w1l wrote: post #132
PragmaticPulp wrote: post #86

Earlier quoted context omitted.

> 2. You “tolerate” this practice just long enough to win the critical initial wave of reviews and benchmarks. Interested buyers will look at those charts for years to come. That’s not what happened here. The AVX-512 instructions not only weren’t enabled by default, they couldn’t be enabled at all unless you went out of your way to disable the efficiency cores completely. They also wouldn’t benefit your workload unle…

Comparing the facts to all the suspicious people here, it made me realize something. Our zeitgeist sure is a cynical one.

Humans seem prone to find meaning and conspiracy amidst chaos and confusing circumstances.
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