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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

#61

Post by flyinghamster »

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.

The Core 2 Quad Q8200 was what did it for me. I had intended to build a system to play with virtual machines, only to find after I built it up that the Q8200 didn't have VT-x - something that was NOT noted in the store display.

I put it in an Intel-branded motherboard as well, and that turned out to be one of the few motherboards I've had that failed prematurely.

Since then, the only Intels I've bought since then have been used ThinkPads.

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

#62

Post by PragmaticPulp »

alkonaut wrote: post #60

Do both E and P cores handle avx instructions or are some instructions specific to p-cores? In that case, how does a processor with heterogeneous cores deal with processes (or, how does the OS/driver do it in automatic mode when affinity isn’t guided)?

Nope! You have to disable the efficiency cores to enable AVX-512. Between that and the relative scarcity of AVX-512 code, this isn’t really a big loss. It wasn’t like it was a free feature.

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

#63

Post by PragmaticPulp »

NavinF wrote: post #22

I’m not surprised. A lot of people were burned last year when their entire CPU downclocked as soon as one application started using AVX-512. That killed all interest even before Alder Lake. Also see Linus’s rants in this thread: https://www.realworldtech.com/forum/?threadid=193189&curpost... And the discussion: https://news.ycombinator.com/item?id=23809335 Today only benchmarks and HPC workloads use AVX-512. I’m sure…

Enabling AVX-512 also requires the efficiency cores to be disabled. A lot of people are getting upset about this, but it wasn’t really a free benefit for anyone except those with very specific AVX-512 workloads that didn’t benefit from the extra cores.

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

#64

Post by 3836293648 »

marcan_42 wrote: post #26
pantalaimon wrote: post #16

Since Linux loads the microcode on it's own, can this be used to apply an old microcode or is there a prevention against downgrading the version?

I'm pretty sure downgrades are blocked. You need to hack the BIOS so the (volatile) upgrade never happens on boot.

Microcode updates are applied at runtime, every time you boot them. At least on the CPU side. The motherboard might apply them before the OS loads though, so who knows what happens there

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

#65

Post by qayxc »

zokier wrote: post #52
qayxc wrote: post #34

Earlier quoted context omitted.

The BIOS doesn't upgrade microcode - the OS does. During boot there's usually no network connectivity, so how would the BIOS even know of an update, let alone acquire it?

The CPU can update its microcode before executing BIOS, the BIOS can do its updates, and then the OS can do its stuff. It's all described in https://www.intel.com/content/www/us/en/developer/articles/t...

That just when the update is applied, not how it gets there.

The FIT is still updated externally (e.g. by the OS) and doesn't magically fill itself with new microcode.

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

#66

Post by phkahler »

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…

>> Very few “evil schemes” exist in reality because people aren’t all that clever

True, but those that try actual evil schemes must be watched for repeats. Remember Intel and Rambus?

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

#67

Post by PragmaticPulp »

marcan_42 wrote: post #38
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.

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 it.

> AMD supports ECC on their consumer chips, but without Intel support it's never taken off

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

Let’s be honest: People aren’t interested in ECC RAM for the average build. I use ECC in my servers and workstations, but I also accept that I’m not the norm.

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

#68

Post by gambiting »

adrian_b wrote: post #50
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.

There was no specification about this feature until immediately prior to launch. When a company announces with years in advance a new product (e.g. Alder Lake), that is the replacement for their previous product (i.e. Rocket Lake & Tiger Lake) and in that series of products the most valuable feature is backward software compatibility and the new product will no longer have this feature, one would expect that the comp…

Sure, but that's a customer expectation vs legal obligation.

Like, my sister bought the new M1 MacBook Air, only to discover that it doesn't support dual external screens - while her previous Air did. So there was absolutely an expectation there that any new MacBook Air would also support dual screens, right?

But, at the end of the day - it is mentioned in the spec sheet. She could have checked. Just assuming that a feature is there is not enough. What's more - if dual screens worked originally, and then they stopped working after an update - that wouldn't be a bait and switch either, it would be a fix to bring the computer back in line with its spec.

And yes, I agree that it would suck.

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

#69

Post by fsflover »

Fnoord wrote: post #42
flatiron wrote: post #33

Earlier quoted context omitted.

I’m waiting for amd to do TB4 so I can get a ryzen framework laptop.

Yeah, AMD Ryzen Framework laptop would be amazing. (Would also have ECC support?) They'd have to license TB from Intel. I don't know about TB4, but TB3 is royalty-free, just gotta pass a certification. TB3 or better would be great for eGPUs in general. Not sure I personally would need TB4. Also, I wonder if Framework would be usable with say Proxmox and macOS (or 'native' Hackintosh?)

> AMD Ryzen Framework laptop would be amazing

Except you cannot disable AMD PSP.

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

#70

Post by gambiting »

antman wrote: post #57
gambiting wrote: post #7

Earlier quoted context omitted.

It was never advertised, and Intel very specifically said AVX-512 instructions will not be available. Some motherboard manufacturers made them available anyway, now Intel is fixing that. It's like buying a car with an advertised speed limiter of 155mph, then finding that actually it can go 170mph, and then the manufacturer fixes the speed limiter with a software update. Yes we know the car could go faster, but the sp…

Good example. It’s like buying a car and finding out it has a nice radio that was not advertised. After a few months the car dealership sends someone to break into the car and rip it off. Fair enough since it wasn’t advertised, right?

Well, breaking into your car is still illegal, so no, not fair enough.

More like you buy a car without paying for a satellite radio(or that feature isn't advertised and isn't in the spec sheet), and then that feature gets removed next time you bring the car in for service. That is absolutely fine.

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