Please forgive my lack of familiarity with PCI express hardware, but I have a question:
All those PCI express devices are all sharing the single v2 lane? Is the PCI express bus a network?
Mini-ITX Seaberry Adds 11 PCIe Slots to a Raspberry Pi
11–20 of 74 posts
Re: Mini-ITX Seaberry Adds 11 PCIe Slots to a Raspberry Pi
#12Please forgive my lack of familiarity with PCI express hardware, but I have a question: All those PCI express devices are all sharing the single v2 lane? Is the PCI express bus a network?
Indeed, PCI Express can be thought of in many ways like Ethernet; you can have switches just like Ethernet, though in almost all cases, PCIe is a local area bus (local to one server/machine), whereas Ethernet is still the king of networks.
Re: Mini-ITX Seaberry Adds 11 PCIe Slots to a Raspberry Pi
#13Once you get to this size and price, there’s no point in using a Pi…there are much more powerful options available.
I can see someone making a very powerful open source WiFi router out of this. The Pi can run passively cooled unlike most Intel or AMD CPUs. You wouldn't be doing any DPI on the network traffic without slowing things down, but this thing with some networking hardware cards could become very interesting to many people.
The cost is too high because it's a niche product, of course, but such a board would be able to replace my home router/server quite capably with a good WiFi antenna and some ethernet ports.
Re: Mini-ITX Seaberry Adds 11 PCIe Slots to a Raspberry Pi
#14Please forgive my lack of familiarity with PCI express hardware, but I have a question: All those PCI express devices are all sharing the single v2 lane? Is the PCI express bus a network?
That's probably the way to think about it. PCIe devices communicate point-to-point over dual-simplex serial connections. If you have something like a Raspberry Pi CM4, which only has a single PCIe lane, then there's going to be a PCIe switch.
Re: Mini-ITX Seaberry Adds 11 PCIe Slots to a Raspberry Pi
#15Once you get to this size and price, there’s no point in using a Pi…there are much more powerful options available.
I can see someone making a very powerful open source WiFi router out of this. The Pi can run passively cooled unlike most Intel or AMD CPUs. You wouldn't be doing any DPI on the network traffic without slowing things down, but this thing with some networking hardware cards could become very interesting to many people. The cost is too high because it's a niche product, of course, but such a board would be able to repl…
There are other platforms that are maybe better suited to that role though. I am not very up to date with the hardware but I remember PCengines being one.
Re: Mini-ITX Seaberry Adds 11 PCIe Slots to a Raspberry Pi
#16Alas PCIe switches were starting to get affordable before the great chipmaker consolidation of 2015-2019 ("and seemingly overnight the cost of these switches increased three-fold"[1]). Now most every PCIe switch is >$6/lane. Even just the 12 lanes here, on an old PCIe generation, is going to be a $72 chip, perhaps more (article: PEX8619 Broadcom PCIe switch, $129, 16 lanes, $8/lane, no stock. Compare versus Microchip…
> If nothing else, there better be some decent PCIe available by then- 8x PCIe 5.0 or better. ARM needs to start doing bandwidth, some day (in places other than server class chips); it's been on USB3.0 for a long long time.
Its not up to Arm to attach PCIe lanes but the chip makers who have been competing with x86 which already offer plenty of PCIe lanes. So far, only apple has bothered to make an Arm CPU which can compete with "PC" hardware. Hopefully AMD will offer something similar.
> Thunderbolt + PCIe would be a great boon for general usability & connectivity. Now that Intel has made it royalty free, now that USB4 already incorporates most of the hard part (packet based switching), it might finally be the time for some real PCIe on chip.
USB4 is based on Thunderbolt 3. Given that Thunderbolt 3 is a mess, I don't have high hopes.
Look at RapidIO or 1394 for examples of better thought out interconnects and protocols. PCIe cant connect CPU's together in a NUMA system whereas RapiIO can. RapidIO also uses Ethernet physical layers so there's parallel development with Ethernet. I honestly don't like USB or contraptions invented by Intel that are invariably consumer grade with various extensions to satisfy other industries, bolted on.
Re: Mini-ITX Seaberry Adds 11 PCIe Slots to a Raspberry Pi
#17Once you get to this size and price, there’s no point in using a Pi…there are much more powerful options available.
I can see someone making a very powerful open source WiFi router out of this. The Pi can run passively cooled unlike most Intel or AMD CPUs. You wouldn't be doing any DPI on the network traffic without slowing things down, but this thing with some networking hardware cards could become very interesting to many people. The cost is too high because it's a niche product, of course, but such a board would be able to repl…
How many networking cards? I know we tend to think of internal buses as infinitely-fast, but a single PCIe 2.x lane is saturated at 500MB/s, which begins to look a little skinny once we're considering 10GE or even Wifi 6.
Re: Mini-ITX Seaberry Adds 11 PCIe Slots to a Raspberry Pi
#18Alas PCIe switches were starting to get affordable before the great chipmaker consolidation of 2015-2019 ("and seemingly overnight the cost of these switches increased three-fold"[1]). Now most every PCIe switch is >$6/lane. Even just the 12 lanes here, on an old PCIe generation, is going to be a $72 chip, perhaps more (article: PEX8619 Broadcom PCIe switch, $129, 16 lanes, $8/lane, no stock. Compare versus Microchip…
> If nothing else, there better be some decent PCIe available by then- 8x PCIe 5.0 or better. ARM needs to start doing bandwidth, some day (in places other than server class chips); it's been on USB3.0 for a long long time. Its not up to Arm to attach PCIe lanes but the chip makers who have been competing with x86 which already offer plenty of PCIe lanes. So far, only apple has bothered to make an Arm CPU which can c…
>So far, only apple has bothered to make an Arm CPU which can compete with "PC" hardware.
Also Amazon: https://aws.amazon.com/ec2/graviton/
Re: Mini-ITX Seaberry Adds 11 PCIe Slots to a Raspberry Pi
#19Please forgive my lack of familiarity with PCI express hardware, but I have a question: All those PCI express devices are all sharing the single v2 lane? Is the PCI express bus a network?
That's probably the way to think about it. PCIe devices communicate point-to-point over dual-simplex serial connections. If you have something like a Raspberry Pi CM4, which only has a single PCIe lane, then there's going to be a PCIe switch.
Interesting, thank you!
Re: Mini-ITX Seaberry Adds 11 PCIe Slots to a Raspberry Pi
#20Alas PCIe switches were starting to get affordable before the great chipmaker consolidation of 2015-2019 ("and seemingly overnight the cost of these switches increased three-fold"[1]). Now most every PCIe switch is >$6/lane. Even just the 12 lanes here, on an old PCIe generation, is going to be a $72 chip, perhaps more (article: PEX8619 Broadcom PCIe switch, $129, 16 lanes, $8/lane, no stock. Compare versus Microchip…
> It feels insane to hope for but I'm really hoping that by the time 2025 rolls around we see some modest affordable arm chips that have Thunderbolt built in. Perhaps even multiple Thunderbolt. If nothing else, there better be some decent PCIe available by then- 8x PCIe 5.0 or better.
In the shorter term, I'm hoping the RK3588 actually comes out, is as good as promised, and has a reasonable price. [1] 4 lanes of PCIe 3.0 + 3 lanes of PCIe 2.0 + 2x USB 3.1 + dual gigabit Ethernet total at well over 10X the bandwidth of the Pi's single PCIe 2.0 lane. Also things I care about for my NVR project: faster video decoding, built-in TPU, and SATA (which I didn't count above because it's multiplexed with the PCIe 2.0).
I don't think the 4x Cortex-A76 + 4x Cortex-A55 is in the same league as the Apple M1, but still quite a bit faster than the Pi4's 4x Cortex-A72.
[1] https://www.cnx-software.com/2020/11/26/rockchip-rk3588-spec...