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Speaking of Raspberry Pi, what's the chance that we'll see a Raspberry Pi 4 within a couple of months with higher bandwidth I/O, like USB 3? The RPi 3 is mostly

Speaking of Raspberry Pi, what's the chance that we'll see a Raspberry Pi 4 within a couple of months with higher bandwidth I/O, like USB 3? The RPi 3 is mostly fast enough for most applications, but the slow USB (and ethernet over USB) makes it unsuitable for networking where any kind of bandwidth is required, like a simple NAS using an external harddrive. I guess it comes down to what kind of chips Broadcomm has at the right price point, anybody here know if it's a possibility?

deleted 10y ago
[deleted]
Const-me 10y ago
Not going to be terribly efficient. There’s no DMA for USB. Meaning, every IP packet has to go through CPU, and the CPU isn’t that powerful. Some people tested gigabit USB NICs with Pi 3. Different people measured 250-300 mbit/sec, way lower than USB 2.0 limit 480 mbit/sec. I think the CPU was the limiting factor there, not the USB.
- sorenjan 10y ago
  Doesn't really need to be terribly efficient, good enough will do for the price. One issue is that there's only one USB port on the board, and the external ports and the ethernet port are connected through a hub. So when you connect an external harddrive and try to transfer data over the network you end up with < 10 MB/s transfer speeds. If Broadcomm decided to use DMA for their USB that would of course be ideal, but I don't know if they have any suitable products like that. Of course 4K and h.265 video decoding would be welcome too for a lot of users.
  - Const-me 10y ago
    Apparently, Raspberry markets their products as affordable but still useful. The features you’re asking for are currently way too expensive for that market. Single-board computers with USB 3.0 and capable of 4K playback are available, but they cost $200 or more: Nvidia Jetson TK1, Inforce 6540, etc.
    - justin66 10y ago
      But that just begs the question: does Broadcom have any parts on the shelf such that, if they tweaked them and sold them to the RPi project at cost, they'd fulfill those requirements? Broadcom and the RPi project can do some things in conjunction that Nvidia, for example, cannot.
      - Const-me 10y ago
        Looks like the answer is yes, this chips are sold for $20: https://www.broadcom.com/products/broadband/set-top-box/bcm7251 https://www.broadcom.com/products/broadband/set-top-box/bcm7... However I’m not much into the hardware design, I only write some embedded software for those things. Might be reasons why it’s still too expensive: if the chip requires too many layers in the PCB, too many external components (like RAM), too much electrical power so it needs better PSU and some cooling, and so on.
  - khedoros1 10y ago
    > One issue is that there's only one USB port on the board, and the external ports and the ethernet port are connected through a hub. More than that: it's not even a USB host port. The silicon is some Synopsys IP called "DesignWare USB 2.0 OTG Controller". The driver implements host mode emulation.
  - brokenmachine 10y ago
    Can rpi not do h265 decoding already? I thought Kodi was popular on the rpi. I was thinking about setting one up as a media player, but not if it can't do h265.
- dmitrygr 10y ago
  1. USB will never give you 480mbps of actual useful data. There is framing, ACKs, retransmits, high level protocol overheads, and such to consider. ~200-300mbps is just about what you'd expect from a USB network connection (depending on packet sizes tested) 2. Most USB controllers do DMA just fine. Maybe you're things of pci-e or firewire-like ability to do a direct write to host ram. That USB lacks (good). But actual DMA for packet data is part of any USB controller nowadays. Even in tiny microcontrollers.
  - beagle3 10y ago
    I regularly get 50MB/s and sometimes a little more from HDDs through USB3 on a PC; that's probably the entire 480mbps once framing and protocol are taken into account
    - dmitrygr 10y ago
      mass storage over usb has much less protocol overhead (you can x-fer 64K without any interruptions) network over usb has smaller frames and more framing. please see specs
- hinkley 10y ago
  Really? Doesn't the Beagle Board support DMA USB? I'm surprised that raspberry doesn't.
jsingleton 10y ago
I'm sure there is another new version in the works. They always keep very quiet about it so as not to damage sales of the current version. Who would have bought a Pi 2 knowing how quickly there would be a Pi 3? There could be a Pi 4 out next week for all we know, unlikely though.
khedoros1 10y ago
In the next few months? Zero. This year, there's the Compute Module 3, and the Pi 3A. Eben Upton said not to expect a Pi4 anytime soon. The bcm2835 (in the Pi1) was chosen for convenience, because of the connections the developers had, and price. The 2836 and 2837 worked out because they were close to drop-in replacements, so when the chip costs came down enough to be affordable, the modifications were relatively minor. To move forward, they'll need to redesign the next board, and at the very least choose a different chip family that includes real USB host hardware.
- sorenjan 10y ago
  I guess that's good and bad news. I would have liked a Pi 4 soon (the pattern seems to be new releases in February), but as far as I've seen it's probably good if they redesign the next version and use something more standard and modern. I guess they're still committed to Broadcomm though. Maybe one of the chinese competitors is a better choice at the moment? I would like an Intel Atom based board, but that doesn't seem viable yet. Maybe they're too expensive, despite Aliexpress and other shops having lots of different Atom based tablets for not even double what a Pi costs.
- makomk 10y ago
  If I recall correctly, the 2836 and 2837 were specifically designed for the Pi so they could be as close as possible to the original. Also, Eben Upton always insists that the next model isn't coming any time soon right up until the launch announcement.

deleted 10y ago

[deleted]

Const-me 10y ago

Not going to be terribly efficient. There’s no DMA for USB. Meaning, every IP packet has to go through CPU, and the CPU isn’t that powerful. Some people tested gigabit USB NICs with Pi 3. Different people measured 250-300 mbit/sec, way lower than USB 2.0 limit 480 mbit/sec. I think the CPU was the limiting factor there, not the USB.

sorenjan 10y ago
Doesn't really need to be terribly efficient, good enough will do for the price. One issue is that there's only one USB port on the board, and the external ports and the ethernet port are connected through a hub. So when you connect an external harddrive and try to transfer data over the network you end up with < 10 MB/s transfer speeds. If Broadcomm decided to use DMA for their USB that would of course be ideal, but I don't know if they have any suitable products like that. Of course 4K and h.265 video decoding would be welcome too for a lot of users.
- Const-me 10y ago
  Apparently, Raspberry markets their products as affordable but still useful. The features you’re asking for are currently way too expensive for that market. Single-board computers with USB 3.0 and capable of 4K playback are available, but they cost $200 or more: Nvidia Jetson TK1, Inforce 6540, etc.
  - justin66 10y ago
    But that just begs the question: does Broadcom have any parts on the shelf such that, if they tweaked them and sold them to the RPi project at cost, they'd fulfill those requirements? Broadcom and the RPi project can do some things in conjunction that Nvidia, for example, cannot.
    - Const-me 10y ago
      Looks like the answer is yes, this chips are sold for $20: https://www.broadcom.com/products/broadband/set-top-box/bcm7251 https://www.broadcom.com/products/broadband/set-top-box/bcm7... However I’m not much into the hardware design, I only write some embedded software for those things. Might be reasons why it’s still too expensive: if the chip requires too many layers in the PCB, too many external components (like RAM), too much electrical power so it needs better PSU and some cooling, and so on.
- khedoros1 10y ago
  > One issue is that there's only one USB port on the board, and the external ports and the ethernet port are connected through a hub. More than that: it's not even a USB host port. The silicon is some Synopsys IP called "DesignWare USB 2.0 OTG Controller". The driver implements host mode emulation.
- brokenmachine 10y ago
  Can rpi not do h265 decoding already? I thought Kodi was popular on the rpi. I was thinking about setting one up as a media player, but not if it can't do h265.
dmitrygr 10y ago
1. USB will never give you 480mbps of actual useful data. There is framing, ACKs, retransmits, high level protocol overheads, and such to consider. ~200-300mbps is just about what you'd expect from a USB network connection (depending on packet sizes tested) 2. Most USB controllers do DMA just fine. Maybe you're things of pci-e or firewire-like ability to do a direct write to host ram. That USB lacks (good). But actual DMA for packet data is part of any USB controller nowadays. Even in tiny microcontrollers.
- beagle3 10y ago
  I regularly get 50MB/s and sometimes a little more from HDDs through USB3 on a PC; that's probably the entire 480mbps once framing and protocol are taken into account
  - dmitrygr 10y ago
    mass storage over usb has much less protocol overhead (you can x-fer 64K without any interruptions) network over usb has smaller frames and more framing. please see specs
hinkley 10y ago
Really? Doesn't the Beagle Board support DMA USB? I'm surprised that raspberry doesn't.

jsingleton 10y ago

I'm sure there is another new version in the works. They always keep very quiet about it so as not to damage sales of the current version. Who would have bought a Pi 2 knowing how quickly there would be a Pi 3? There could be a Pi 4 out next week for all we know, unlikely though.

khedoros1 10y ago

In the next few months? Zero. This year, there's the Compute Module 3, and the Pi 3A. Eben Upton said not to expect a Pi4 anytime soon. The bcm2835 (in the Pi1) was chosen for convenience, because of the connections the developers had, and price. The 2836 and 2837 worked out because they were close to drop-in replacements, so when the chip costs came down enough to be affordable, the modifications were relatively minor. To move forward, they'll need to redesign the next board, and at the very least choose a different chip family that includes real USB host hardware.

sorenjan 10y ago
I guess that's good and bad news. I would have liked a Pi 4 soon (the pattern seems to be new releases in February), but as far as I've seen it's probably good if they redesign the next version and use something more standard and modern. I guess they're still committed to Broadcomm though. Maybe one of the chinese competitors is a better choice at the moment? I would like an Intel Atom based board, but that doesn't seem viable yet. Maybe they're too expensive, despite Aliexpress and other shops having lots of different Atom based tablets for not even double what a Pi costs.
makomk 10y ago
If I recall correctly, the 2836 and 2837 were specifically designed for the Pi so they could be as close as possible to the original. Also, Eben Upton always insists that the next model isn't coming any time soon right up until the launch announcement.