Pi Cluster vs. Ampere Altra Max 128-Core ARM CPU | Hacker News Reader

Pi Cluster vs. Ampere Altra Max 128-Core ARM CPU

jeffgeerling.com

48 pointsingve15 comments

One of the big issues I have with ARM CPUs right now is that you can’t really purchase them anywhere as a consumer. They consolidate everything into the hands of a few major players, while hobbyists are relegated to sticking with x86. I wonder if RISC-V is going to fix that.

I agree. It makes building and testing arm64 versions of larger software a real pain. I do personal builds of llvm + clang + rust on a couple of 8GB RPi4s, but it takes many hours. I built a 1U 5900X build machine for about £1500 a couple of years ago. I'd happily spend similar on a 1U arm64 box, but as far as I can see, I can only buy something spectacularly higher spec with a spectacularly higher price tag, or an SBC which is an order of magnitude slower than a modern amd64.

Perhaps arm64 Macs running Linux will be one answer, but unless I'm badly misreading the documentation and status updates, you still can't blow away the MacOS and Recovery partitions because recovery MacOS is needed for some maintenance tasks such as updating the stage1 m1n1, which makes me very uncomfortable. (I'd be so happy to be corrected if that's no longer the case though!)

macOS Recovery will always be required. The boot firmware on those machines doesn’t have any kind of user interface. When you long click on the power button, you are reaching macOS Recovery, which has a Boot Picker app running.

tldr: consider macOS Recovery as part of the boot FW.

Ouch, that's really horrible - and presumably signing makes it impossible to replace the MacOS recovery with a linux kernel + initramfs to act as recovery UI?

Thanks for clarifying. Looks like that's another route to a clean, fast arm64 machine to cross off the list. :(

Is one of these machines completely bricked if you wipe the entire SSD including recovery partition, or is the recovery in a separate write-protected flash area that you can't wipe even if you try?

Those machines have a boot ROM recovery mode. If you wipe off those essential partitions then it becomes visible as a USB device when attached to a Mac or PC.

On Linux, you can then use idevicerestore to recover. Or you can use Configurator from a Mac.

macOS Recovery is an essential part of the security model.

It is the environment that you can do security downgrades from (to disable Secure Boot for your OS install notably). macOS on Apple Silicon uses per-OS security policies instead of a global machine one, allowing to have an unsecured install and a secured one at the same time, with just a reboot needed. As such, macOS Recovery cannot be modified.

I'd expect RISC-V to make that problem worse since you don't even need a license to vertically integrate it.

Is the 500 watt figure for the Ampere Altra Max a mistake? Everything else I've read says that it has a TDP of 250 watts.

Could the figures be representing total system power draw?

250w of non-processor overhead would still be atrocious.

Yeah, in this case it's the total system power for that Supermicro server, not CPU direct. (That made comparing it to the Pi cluster and other systems easier.)

250w of overhead seems inexplicably high; my old supermicro dual CPU Xeon E3 server crammed full of 12 HDDs and 24 sticks of 32GB LP ECC has 100w of overhead + 35w per CPU for a total draw of 170w.

I agree. My Gigabyte Ampere system idles closer to 120 watts total, including the disks. While it's not filled to the brim with RAM, 250 watts seems high.

Maybe it has two CPU sockets?

I'd guess that the unified memory on the Mac makes the performance so good.

M1 Max does seem to have good memory bandwidth, which probably helps. If they were running code on the GPU then the unified memory architecture might help as well.

Interesting that that the Mac benchmark results are from Docker, i.e. running on a virtualized Linux kernel.

Newer versions of Docker for Mac, running with ARM64 Linux instances, lets you pass through all 10 CPU cores (and in my case 32GB of RAM), and doesn't impose much performance penalty really.

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