Arm Announces Cortex-A78, Cortex-X Custom

[PerformanceExpert]

Since L1 cache is the fastest memory in the system (save for registers), it's also the most power hungry.
And yes, efficiency is at odds with performance. When one wins, the other one loses.

It's never either/or. Like with software, hardware is not 100% optimal, so there is always plenty room for improvement of every aspect. You can improve performance and get better efficiency. For example, replace the branch predictor with a larger one that uses the same amount of power. Your performance improves due to fewer branch mispredictions, and as a result your efficiency improves. Similarly improve efficiency and as a result performance improves in power constrained scenarios.

[L_A_G]

Umm... The Cortex-series are not SoCs, but CPU cores sold as IP cores (i.e designs ready-fort-synthesis laid out in Verilog/VHDL) to various companies who make SoCs. To call them as such is like calling a Yamaha engine a "car" when they're just component parts that Yamaha makes based on design specs given to them by carmakers like Volvo and Toyota.

I see they're just going bigger and bigger with these cores in terms of transistors per core. Some size growth is completely natural, but it feels like ARM is now very much aiming at continually growing the cores until they have a real desktop replacement in their hands. All the while my current phone uses four comparatively tiny A53 cores and I don't think I need anything considerably faster.

[bug77]

Since when is halving the L1 cache size an ..."improvement"?

I guess when cpu manufacturers raise it they claim it's a performance improvement and when they reduce it they claim it's an efficiency improvement... They can never lose

Since L1 cache is the fastest memory in the system (save for registers), it's also the most power hungry.
And yes, efficiency is at odds with performance. When one wins, the other one loses.

[torsionbar28]

Security is important in the mobile space. However, like on your PC, by far your biggest risk is not from a Spectre-style attack but from downloading an app with a virus or clicking on a link a "friend" sent. If you avoid that, there is generally little to worry about. A long time ago, I connected my brand new Windows PC to the internet and got infected with a worm within 5 minutes due to the total lack of security at the time. Things changed.

This, plus the actual volume of mobile malware in the wild is very low. I have Android phones from ~2014 that I've *tried* to infect with Android malware and was unsuccessful. Side channel attacks like Spectre are more the territory of nation state actors (and it's a large effort, even for them), pretty far removed from the petty crooks and organized crime who want to pilfer your wallet. It's not worth losing any sleep over.

Agreed 100% that it's your personal behavior (clicking malicious links, loading malicious apps, etc.) that is by far the biggest threat to mobile device security. Use common sense, and you'll be fine.

[_Alex_]

Well, then why have multiple layers of caches? Just put everything in L1.

Its a balance of size/speed (bigger cache = slower access) and power(-efficiency), and the sum is that the chip is now balanced differently and in sum is faster than its predecessor.

I'm just mentioning the PR rationale behind these moves. I mean whatever they do, they always tout it as an improvement. Whether the cache goes up or down, well... you guessed it: It's always an improvement

[PerformanceExpert]

I still don't trust banking, insurance and some communication applications and I can't be a responsible/productive member of modern society without those. I use my mobile device for two factor authentication, so from a professional and ethical perspective it's extremely important for my device to be secure from top to bottom.

Security is important in the mobile space. However, like on your PC, by far your biggest risk is not from a Spectre-style attack but from downloading an app with a virus or clicking on a link a "friend" sent. If you avoid that, there is generally little to worry about. A long time ago, I connected my brand new Windows PC to the internet and got infected with a worm within 5 minutes due to the total lack of security at the time. Things changed.

[torsionbar28]

I have my hopes up for RISC-V but standardizing it will be a massive challenge.

The only demand for RISC-V in the visible future is in closed proprietary embedded devices, if at all. As much as I'd like to see a completely open RISC-V commodity board in a standard PC form factor (e.g. ATX) I think this is a pipe dream and it will never ever materialize. A laptop based on the same is even further out.

The potential is there, but the market demand isn't. Maybe a one-off amateur grade kickstarter or something like that. The demand is lower than commodity Power boards (aka Talos & AmigaOne), so I would expect the per-board cost to come in quite a bit higher. Would you pay $2750 for a totally open commodity RISC-V board? Yeah, me neither. Turns out its actually quite expensive to design and build a motherboard, regardless of which CPU type goes into it.

[Jabberwocky]

Probably still more secure than processors from Intel and AMD because ARMv8 is such an effective architecture (unlike the shitty x86 architecture) so it doesn't even need symmetric multithreading (SMT) aka HyperThreading, so it doesn't suffer from all those Meltdown, Spectre, etc vulnerabilities.

Except that many ARM cores are vulnerable to Spectre. Here's the proof: https://developer.arm.com/support/ar...-vulnerability

In theory I am pro RISC, albeit it's sad that so many of my ARM devices are not longer supported. The legacy support from x86 has been very useful over the decades. I have my hopes up for RISC-V but standardizing it will be a massive challenge. I am curious what https://nuviainc.com/ will release although they are not targeting consumers. I'm loving all the competition and innovation coming back.

Actually, in mobile space it doesn't matter that much,... There are worse security vulnerabilities in OS, and you should use applications you trust, anyway. For server/cloud side, where there's lots of virtualization (or containers), security against side channel attacks is more important.

I agree that attackers will target server/cloud because they stand more to gain. However just because it's more important there doesn't mean that it's not important in mobile space. I still don't trust banking, insurance and some communication applications and I can't be a responsible/productive member of modern society without those. I use my mobile device for two factor authentication, so from a professional and ethical perspective it's extremely important for my device to be secure from top to bottom.

A few years ago you could still choose which applications you wanted to use. For example, I ran a Windows VM just for my tax submissions (they are still using active-x /w internet explorer). Today it's not that simple, mobile stores/applications detect that you are running custom operating systems and denies access. If you don't have certified iOS or Android you're simply out of luck and if you use certified OS you're open to many attack vectors.

I am seriously considering getting a PinePhone just for contact info and two factor authentication.

[discordian]

Since when is halving the L1 cache size an ..."improvement"?

I guess when cpu manufacturers raise it they claim it's a performance improvement and when they reduce it they claim it's an efficiency improvement... They can never lose

Well, then why have multiple layers of caches? Just put everything in L1.

Its a balance of size/speed (bigger cache = slower access) and power(-efficiency), and the sum is that the chip is now balanced differently and in sum is faster than its predecessor.

[_Alex_]

Since when is halving the L1 cache size an ..."improvement"?

I guess when cpu manufacturers raise it they claim it's a performance improvement and when they reduce it they claim it's an efficiency improvement... They can never lose