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Comment by kart23 | Hacker News Reader

This is cool. Whats really holding it back at this point is it's use of a sd card.

I find that its pretty difficult to use 4gb of ram on a pi practically, and its often bottlenecked by I/O. It might just be my SD card, but executing trivial commands sometimes takes forever and reminds me that I'm in a pi. I've heard ssds can improve speeds a lot, but you still cant boot off usb.

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USB boot is coming, beta started a week ago:

https://www.raspberrypi.org/forums/viewtopic.php?t=274595

Here's a video tutorial on how to utilise this to boot on an SSD by an awesome small electronics hacker:

https://youtu.be/zVhYvvrGhMU

I'm surprised no one is getting excited for pxe boot.

That's a game changer.

That’s been available on earlier versions of the Pi (2B v1.2, 3B, 3B+).

It was not available at launch for the Pi 4, but was released in beta firmware in late September, and is currently part of the critical firmware update.

It works well, allowing separate boot images for each individual Pi on your network.

> It works well, allowing separate boot images for each individual Pi on your network.

Isn't that a natural capability with PXE implemented at the server keyed off the MAC address?

I’m sure that’s true. I’ve only used this for Rpis, which have it as a neat pull-based capability. Just add a subdirectory with the right name for each one in the tftp root.

That's how it works for other PXE boot as well...

yup, i tried netbooting on the 3b+, with root on nfs and without an sdcard.

> It works well, allowing separate boot images for each individual Pi on your network.

could you elaborate a bit more on that?

Intel should be making an Optane sdcard for embedded use, potentially with a built in power down capacitor to make sure all acknowledged writes make it to Optane.

When using netboot, the boot rom will pull the files it needs from the tftp server. It will first look for them in a subdirectory with the Pi’s serial number as its name.

If you’re netbooting without any sdcard installed, I’d suggest disabling sd polling.

PXE uses the MAC address doesn't it?

It does, but I think what the Pi does is connect to the TFTP server handed out by PXE and then look for a folder named serial-number. If it doesn't exist in the path PXE gave it it just boots whatever is in the tftproot.

Might or might not. It does DHCP request and server-side, you can do decision on what it returns on any tag you want, often client architecture (0x93); you can then point to the right tftp server, or if you have UEFI client, you can also use http.

You actually can boot straight from USB as of very recently.

Something you've always been able to do is to keep just the boot partition on a small SD card and the root on whatever USB device you like. And yes, even with the supposedly best-performing SD cards, they easily become a problem both with performance and failure.

> You actually can boot straight from USB as of very recently.

IITC that is still not officially supported (as a beta-test feature?), though many report it works as intended.

In the meantime if people don't want to use a beta feature the boot-from-SD-mount-root-elsewhere option works well too. You could also run it of an NFS share instead of a USB stick, though the performance metrics will differ.

I also read recently that the lack of cooling can really throttle the performance of a Pi4. Do you have a good heat sink and fan installed?

The RPi4 was designed with bursts of activity in mind, but for more sustained work without thermal throttling I have had very good experiences with the Argon One case (https://www.argon40.com/catalog/product/view/id/52/s/argon-o...) and the Flirc case (https://flirc.tv/more/raspberry-pi-4-case).

Does the Argon One fan push air through the case? In the pictures it looks like it just circulates air inside the case over the CPU.

I did an article on the topic after the Pi firmware update made the situation a lot better. A bare Pi is okay without a fan, but if you want it in a case, the Flirc case is your best option (IMO): https://www.jeffgeerling.com/blog/2019/best-way-keep-your-co...

Great article, thanks. The Flirc case looks good and for $15 it's an obvious buy.

Having just spent a bit north of $1k on a new CPU, RAM, and mobo for my desktop, I'm having a bit of sticker shock (in a good way) at how low these RPi prices are.

A year or so later, you think back "how did I accumulate a box full of Raspberry Pis?" And "I had no idea I had this many power supplies!"

For my use case, I need access to the GPIO pins. The blurb on the Flirc says that access is possible but I don't see any opening. Can you confirm that GPIO access I possible?

I use this case: https://shop.pimoroni.com/products/aluminium-heatsink-case-f...

Doesn't look as flashy as the Flirc case, but cooling performance is supposed to be similar and you can access all the pins.

The gpio access requires a header cable routed out a slot in the base of the case.

I have several pi in flirc cases, one is a pihole and one runs CI jobs (slowly) for PhotoStructure, and they don't get too hot even under sustained cpu load.

Flirc cases are great.

If you don't want to think about thermal throttling ever again, get one of these:

https://www.seeedstudio.com/ICE-Tower-CPU-Cooling-Fan-for-Ra...

Isn't that overkill? When are we going to start liquid cooling our raspberry pis? I expect someone to tell me that's already a thing....

Of course it is:D

https://hackaday.com/2017/05/15/liquid-cooling-overclocked-r...

https://modmymods.com/water-cooling-kits/raspberry-pi-coolin...

I have a fan shim on mine, and it keeps it well within limits. The shim is controlled by the on die temperature, so it runs slowly most of the time, but if you run the CPU/GPU hard for any length of time, the fan really cranks up. You have to add a driver to have the automatic control.

I had a passive aluminum block heat spreader on it, and that works if you have good thermal bonding, unless you are really working it for a long duration. The problem is, if you hammer it long enough to throttle, that same mass takes a long time to cool back down.

The fan shim on a naked card just seems to work.

https://shop.pimoroni.com/products/fan-shim

I would like to see one of those wicked vapor cooled heat pipes on a spreader built for the Pi.

I have this heatsink on it, and I've never seen the cpu temps above 60C. It gets hot, but I think it does the job.

https://shop.pimoroni.com/products/aluminium-heatsink-case-f...

I have the same case and share your opinion. It gets warm, but CPU temperature is well within limits. And somehow the idea of passive cooling is very attractive.

With a $10 case/fan combo mine idles around 30c and hits about 60c under load (this is in a room at about 21c). The Pi doesn't start throttling til about 80c

Could this be fixed by setting aside a few gb of RAM for a virtual RAM drive, and run the OS from there?

It's fairly trivial to build an entire OS into an initramfs to run from memory. Also, the poor performance of most microSD cards is primarily due to their flash quality, and designed use case in phones and cameras for external storage. Using a quality thumb drive or SSD over USB 3.0 would yield substantially better performance.

The OS uses free RAM as a cache for file reads anyway. Temporary directories that are not meant to persist after reboots are often mounted as a ramdisk however.

I've gone for an SSD over USB3, and get good performance - though RAMdisk would certainly be faster still and feasible with 8GB.

Running from RAM would also be great for having an effectively static system -- just reboot to get a clean slate; the hardware storage needn't even be available after boot.

IIRC this is the default mode of operation on the Alpine Linux version for the Pi.

there was this posted a few days ago: https://www.tomshardware.com/how-to/boot-raspberry-pi-4-usb

This is one thing I always appreciated more about the BeagleBone but the Pi being more popular I've gone with it as my main SBC of choice for obvious reasons. The Pi has always been cheaper as well.

I totally agree. Even spinning rust leaves “fast” microsd cards in the dust. I hope they can manage to give us m.2 slot in the future.

A new spec for microSD cards (microSD Express) was announced last year, which would let them use similar protocols to SSDs. I don't know if this means they'll support things like TRIM, without which their performance may initially be fast but degrade over time. Still, it would be a significant improvement.

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