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Raspberry Pi PCIe Devices

pipci.jeffgeerling.com

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Re: Raspberry Pi PCIe Devices

#51

Post by exabrial »

parsimo2010 wrote: post #50
exabrial wrote: post #44

what??? I _did not know_ PCI-E was exposed! I literally just had another discussion on HN a few weeks back when someone posted a 3d printed PI Cluster, and everyone lamented how lame storage latency was on a PI. I guess we're all pretty ignorant of the current offerings!

This is pretty recent. The USB controller on the regular Pi 4 was sitting on the PCIE lines, so until the CM4 came out the only way to get to PCIE was to lose USB support and solder wires onto the traces on the PCB. A couple people did it but not many. Most people could get by with a USB 3.0 accessory and didn’t need to cut up their Pi. But now that the CM4 has a PCIE slot on the daughterboard it makes sense to see w…

Ah, that was going to be my followup question. I'm having trouble finding a block diagram of the CM4 (and RPI4), if you happen to have a link, that'd be incredible.

* Also, how the Ethernet PHY connect to the CPU and what are the implications?

Re: Raspberry Pi PCIe Devices

#52

Post by wrs »

moron4hire wrote: post #36
jchw wrote: post #12

Earlier quoted context omitted.

I read the first sentence of this post without noticing your username and thought, “wait, wasn’t that marcan?” — of course it was :) It’s a good time to rewatch that classic talk (and probably some other old ccc talks, there’s a wealth of great ones.)

This is something that I miss about forums of yore and sort of hate about HN, Reddit, and their ilk: the deprioritization of a post author's identity. I miss being able to scan through a forum's post listing and readily pick out names of posters I recognized after being involved in the site for a while. It was an additional signal of post quality (or lack thereof, depending on the user). Here, the username is hidden…

I think it’s always been that way on HN—it could just be arbitrary, not a deliberate choice. I have noticed around here that if you indicate you might use someone’s identity or history as a signal of quality, you’ll get a lot of “argument by authority” backlash. (Except in the cases of someone who built the thing you’re talking about, and tptacek. :) )

Re: Raspberry Pi PCIe Devices

#53

Post by MisterTea »

nicolaslem wrote: post #49
MisterTea wrote: post #43

Earlier quoted context omitted.

Those need m.2 B key slots which are not compatible with m.2 M key NVMe disks. This is why I'm not crazy about the m.2 "standard".

To be fair the same thing can be said about its predecessor the miniPCIe slot.

True but that was only really for the msata version. m.2 has about half a dozen keys as of now. Like USB-C it tries to cram too many mutually incompatible electrical interfaces into one plug.

Re: Raspberry Pi PCIe Devices

#54

Post by nuclearnice1 »

exabrial wrote: post #44

what??? I _did not know_ PCI-E was exposed! I literally just had another discussion on HN a few weeks back when someone posted a 3d printed PI Cluster, and everyone lamented how lame storage latency was on a PI. I guess we're all pretty ignorant of the current offerings!

Go back and double check! kingosticks replied to you with exactly this link.

Re: Raspberry Pi PCIe Devices

#55

Post by geerlingguy »

wrs wrote: post #52
moron4hire wrote: post #36

Earlier quoted context omitted.

This is something that I miss about forums of yore and sort of hate about HN, Reddit, and their ilk: the deprioritization of a post author's identity. I miss being able to scan through a forum's post listing and readily pick out names of posters I recognized after being involved in the site for a while. It was an additional signal of post quality (or lack thereof, depending on the user). Here, the username is hidden…

I think it’s always been that way on HN—it could just be arbitrary, not a deliberate choice. I have noticed around here that if you indicate you might use someone’s identity or history as a signal of quality, you’ll get a lot of “argument by authority” backlash. (Except in the cases of someone who built the thing you’re talking about, and tptacek. :) )

On the flip side, on HN I like that the author is kind of greyed out. I never notice it until after I read comments if I look for it, so I generally don't even notice the OP or a comment author.

Other sites like Reddit add little icons and highlights in many places that make the username much more prominent.

Re: Raspberry Pi PCIe Devices

#56

Post by geerlingguy »

OJFord wrote: post #41

It's a shame there isn't something between the Model B and the Compute Module, like the CM but with a built-in PCIe header say. There have been a few popular submissions using multiple Pis in clusters recently, really the only reason not to use CMs there js the complexity of the (limited) IO that is needed, and the CM development board (for each one) dominates the cost and would be motr expensive than Model Bs.

There are a few addon boards (for $15-30, most shipping after the new year) that take the CM4 that extra mile: https://github.com/geerlingguy/raspberry-pi-pcie-devices/iss...

I'm most excited about a few with mini PCIe or M.2 slots on the bottom.

Re: Raspberry Pi PCIe Devices

#57

Post by geerlingguy »

tyingq wrote: post #30
mikece wrote: post #28

My first thought was "can you boot from a PCIe SSD?" (looks like the answer is "no" from what I see). I wish there was a RPi with 16GB or 32GB of storage soldered to the board. Where I work we're using Raspberry Pi devices for industrial use and corruption of/wearing out the microSD card has been something we've wondered about. We could just buy premium microSD cards but having a "proper" SSD soldered to the board wo…

There's the compute module...32GB of eMMC is an option. https://www.raspberrypi.org/products/compute-module-4/?varia...

And in some good news on that front, the eMMC storage on the CM4 is twice as fast in many cases as older generations of Pi CMs, as it uses the full 8 bit eMMC bus. It's finally faster (for random IO at least) than any microSD card I've tested.

Re: Raspberry Pi PCIe Devices

#58

Post by geerlingguy »

Namidairo wrote: post #16
sitkack wrote: post #2

Where do we recommend new PCIe devices for you to test? Have you tried Mellanox Infiniband and RDMA?

Wouldn't you saturate the bus fairly easily with a Mellanox card? I can't imagine the experience would be optimal.

From all my testing, it looks like the maximum throughput you can get on the entire PCIe x1 gen 2 lane on the CM4 is about 3.2-3.4 Gbps.

But that's still better than the current maximum of 1 Gbps over Ethernet, or the ~3 Gbps I have tested through a USB 3.0 card.

Re: Raspberry Pi PCIe Devices

#59

Post by robotnikman »

mikece wrote: post #28

My first thought was "can you boot from a PCIe SSD?" (looks like the answer is "no" from what I see). I wish there was a RPi with 16GB or 32GB of storage soldered to the board. Where I work we're using Raspberry Pi devices for industrial use and corruption of/wearing out the microSD card has been something we've wondered about. We could just buy premium microSD cards but having a "proper" SSD soldered to the board wo…

There are MicroSD to CD card adapters out there. A bit clunky but they allow you to use full sized SD cards, which might be more durable
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