10-core i9-10900F desktop CPU lags behind 8-core Ryzen 9 4900HS mobile APU • Hacker News Board

Re: 10-core i9-10900F desktop CPU lags behind 8-core Ryzen 9 4900HS mobile APU

#121

Post by wahern » Fri, Apr 17, 2020, 12:11 AM UTC

SomeoneFromCA wrote: post #117

wahern wrote: post #115

Earlier quoted context omitted.

Hyperthreading (SMT) is the most fruitful vector for side-channel leaks because so many processor resources are shared between the threads. This was the case even before Spectre. Conceptually it's also the easiest vector to mitigate in the OS--simply schedule processes in different trust domains (e.g. different UIDs) on different physical cores. This is what good VM hypervisors do. You'll never be scheduled on a phys…

Right, I understand it is not good in the cloud environments, but how exactly would you exploit it on a desktop Linux computer?

JavaScript and WebAssembly. See MDS (https://en.wikipedia.org/wiki/Microarchitectural_Data_Sampli...), a non-exclusive class of vulnerabilities of which ZombieLoad was but one proven exploit, Portsmash (https://www.theregister.co.uk/2018/11/02/portsmash_intel_sec...), and others.

Here's a good paper (pre Spectre) that surveys various timing attacks and how they relate to specific architectural features: Qian Ge, Yuval Yarom, David Cock, and Gernot Heiser, "A Survey of Microarchitectural Timing Attacks and Countermeasures on Contemporary Hardware", https://eprint.iacr.org/2016/613.pdf.

Re: 10-core i9-10900F desktop CPU lags behind 8-core Ryzen 9 4900HS mobile APU

#122

Post by 2OEH8eoCRo0 » Fri, Apr 17, 2020, 12:21 AM UTC

3fe9a03ccd14ca5 wrote: post #25

These mobile APUs are amazing. Especially when combined with a GPU. It would be really nice to be able to use these in a standard ATX motherboard because it would make the perfect home server CPU.

My home server is a Dell Latitude with an i5-2520M

$80 on craigslist 3 years ago.

Re: 10-core i9-10900F desktop CPU lags behind 8-core Ryzen 9 4900HS mobile APU

#123

Post by titzer » Fri, Apr 17, 2020, 2:13 AM UTC

rasz wrote: post #21

briffle wrote: post #2

Does this new intel CPU have 'fixes' for all issues like spectre and meltdown, where you were supposed to turn off hyperthreading for better security? I'm just curious if the fixes for those (and other similar vulnerabilities) are starting to make their way into silicon, but also that the fixes recommended usually slow cpu's down quite a bit too.

Intel "fixes" so far has been microcode level detectors for particular proof of concepts submitted by researchers. Makeup on a pig. https://www.nytimes.com/2019/11/12/technology/intel-chip-fix...

> microcode level detectors for particular proof of concepts

No, they don't have enough microcode space for this, and the data paths in the CPU that Spectre and Meltdown affect are not programmable with microcode. The microcode updates have been hamfisted, usually amounting to a massive hammer. E.g. the first "hardware fix" for variant 2 (branch target injection) was to make the BTB not shareable across hyperthreads. The fix worked. It was to completely disable the BTB for indirect branch predictions altogether. Ha! That'll confound any sharing of it!

Intel's CPUs are completely riddled with side channels due to the way they implemented speculative rollback. They are kind of screwed.

Re: 10-core i9-10900F desktop CPU lags behind 8-core Ryzen 9 4900HS mobile APU

#124

Post by titzer » Fri, Apr 17, 2020, 2:19 AM UTC

flatiron wrote: post #65

theevilsharpie wrote: post #56

Earlier quoted context omitted.

> Despite the protestations of l33t Cyberhaxxing Z3r0 Cools everywhere, you only have to turn off hyper-threading if you are sharing a machine with someone you don't trust. If you're reading this reply, you probably automatically executed `hn.js`. Are you _sure_ you know what it does? Unless you're browsing the web with Javascript completely disabled, and you also don't have any applications that automatically update…

Are you aware of any spectre POC that in JavaScript you can break out of that sandbox and do anything worth while?

Spectre does not allow write access to unprivileged memory; you need another exploit for that. Spectre allows read access to essentially all of the containing process's address space. This is enough for just leaking secrets, but can also assist with other vulnerabilities, e.g. reversing address space randomization in order to figure out where to write in memory with the other vulnerability. It makes all write exploits more dangerous.

Re: 10-core i9-10900F desktop CPU lags behind 8-core Ryzen 9 4900HS mobile APU

#125

Post by darkteflon » Fri, Apr 17, 2020, 2:54 AM UTC

SomeoneFromCA wrote: post #105

baybal2 wrote: post #95

Earlier quoted context omitted.

Yes, Intel's "marketing TDP" is a complete sham. You get completely different digits once you get full engineering datasheets under NDAs. Intel's 5W "ultraportable" CPUs for examples go to 17W. 15W ones can boost well above 40W.

Interestingly, it was not like that previously. I'd say it slowly started with Haswells. Sandy and Ivy were often less power hungry than their TDP suggested.

I don’t think this is about power efficiency, but thermal envelope.

Re: 10-core i9-10900F desktop CPU lags behind 8-core Ryzen 9 4900HS mobile APU

#126

Post by rubatuga » Fri, Apr 17, 2020, 4:41 AM UTC

1996 wrote: post #78

3fe9a03ccd14ca5 wrote: post #25

These mobile APUs are amazing. Especially when combined with a GPU. It would be really nice to be able to use these in a standard ATX motherboard because it would make the perfect home server CPU.

I share your interest for a silent yet powerful homeserver. Unfortunately, there doesn't seem to be any desktop motherboards for mobile zen2 yet. Too bad. I would even settle on a NUC.

I've found the HP Z230 SFF to be very silent and available for only ~$150.

Re: 10-core i9-10900F desktop CPU lags behind 8-core Ryzen 9 4900HS mobile APU

#127

Post by _bxg1 » Fri, Apr 17, 2020, 5:10 AM UTC

Havoc wrote: post #98

I really appreciate this entire race frankly. For a desktop computer even mid tier 3700X is now "good enough" even for someone with aspirations towards solid gaming. On home use front CPUs seem to have outsprinted their usage cases.

For gaming in particular, the GPU is almost always the bottleneck. It's much easier to throw in more polygons and texture pixels than it is to come up with bigger and more complex gameplay simulations. I'm still running a quad-core i5 from 2014 in my gaming desktop and it rarely has an impact.

Re: 10-core i9-10900F desktop CPU lags behind 8-core Ryzen 9 4900HS mobile APU

#128

Post by [deleted] » Fri, Apr 17, 2020, 5:45 AM UTC

aftbit wrote: post #111

greggyb wrote: post #85

Earlier quoted context omitted.

Intel's is roughly "the thermal dissipation required to maintain base clock speeds indefinitely without thermal throttling". AMD's is roughly "the thermal dissipation required for all-core turbo indefinitely". In recent generations (since AMD's Zen architecture), AMD is much closer in testing to their published numbers than Intel is. It is important to note that this is a thermal specification, rather than a power co…

>There are processors that exist which can hit their performance numbers without needing any thermal solution, and as such would have an "honest" TDP of 0, despite having a >0 power draw from the wall. Nitpick warning - I assume you mean that they are passively cooled in free air. They are still emitting heat into their environment. If you stuck such a processor into a perfectly insulated container, it would eventual…

[deleted]

Re: 10-core i9-10900F desktop CPU lags behind 8-core Ryzen 9 4900HS mobile APU

#129

Post by _ph_ » Fri, Apr 17, 2020, 6:29 AM UTC

jakogut wrote: post #109

_ph_ wrote: post #82

Is there a 4900HS laptop around already that can be recommended for Linux usage?

Reading this now on a ROG Zephyrus G14 ($1,449)[1] running Arch. I've had a few random lockups with Linux 5.6.4, though they seem to have become less frequent with amd-ucode and a bios update. Additionally, I haven't had any problems with 5.7rc1, though the proprietary Nvidia driver (440.82) doesn't compile with that kernel yet. Otherwise, it's been running great. The screen looks great, the touchpad feels really goo…

The machine definitely looks tempting, but based on the mostly failed attempts by Ars Technica to run Linux on it, I had stopped looking at it. But perhaps the kernels they used were too old. Still, for that price, I would expect it to work without issues, as I really would buy it as a Linux machine. How is your experience, Ars had problems with the fans running too high and the battery not lasting as long as it should?

Re: 10-core i9-10900F desktop CPU lags behind 8-core Ryzen 9 4900HS mobile APU

#130

Post by vijaybritto » Fri, Apr 17, 2020, 6:59 AM UTC

NicoJuicy wrote: post #100

vijaybritto wrote: post #72

Earlier quoted context omitted.

I think Apple is already in the process of making their own chips. I'm thinking that they'll release an ARM chip for laptops. They are already blazing out on the mobile side.

I'm actually rooting/hoping for AMD. They seem to be top of the line atm. I haven't seen much of ARM

Yeah using AMD chips can instantly reduce the price and also offer more performance per dollar. Apple should try a single device at least