Groups | Search | Server Info | Keyboard shortcuts | Login | Register [http] [https] [nntp] [nntps]

Groups > comp.sys.raspberry-pi > #9779

Re: rPi and USB 3.1 w/ type C connector

Show all headers | View raw

On 10/7/2015 6:11 AM, Theo Markettos wrote:
> rickman <gnuarm@gmail.com> wrote:
>> On 10/6/2015 4:04 PM, Jonathan Lane wrote:
>>> Dom <domafp@blueyonder.co.uk> wrote:
>>>> On 06/10/15 16:02, rickman wrote:
>>>> Not going to happen. At least for quite some time. It would need a
>>>> completely new SoC design, rather than the minor redesign that was made
>>>> for the Pi 2.
>>> It would also need significantly more expensive silicon.  8xUSB3 changes
>>> the equation from "$25 SBC" to "something with PCIe-bus equivalent
>>> bandwidth for peripherals".  I'd just be happy with a redesign that
>>> moved the ethernet PHY and the storage devices off the USB hub.
>>
>> I don't follow this.  If every part of the I/O were inside the SoC, why
>> would that be more expensive?  Don't you think the internal busses of a
>> 700 MHz processor can keep up with a 5 Gbps serial bus?  32 * 700 MHz is
>> 22.4 GHz.  Regardless, only the video has to run at particularly high
>> rates.  The rest of the peripherals are relatively low average rates
>> with high burst rates.  An SoC is only limited by it's memory band
>> width.  Why would the SoC be any more expensive?
>
> There are several parts to this:
>
> Switching to the Synopsys USB 3.0 or 3.1 IP will cost substantially more
> in licensing fees than the USB 2 IP which is a mature product

Can you substantiate this?  I couldn't find anything indicating this. 
Why do you say "Synopsys USB"?  Surely they aren't the only provider of 
USB IP.


> The USB 3 IP may be targeting a smaller process (22, 28nm?).  The PHY is
> substantially different.

Other than the PHY, IP typically doesn't target a process.  Even if it 
does, a smaller process is usually less expensive for the chip.  That's 
why they continue to shrink the feature size.


> The above assumes SuperSpeed (5Gbps) or SuperSpeed+ (10Gbps).  It's possible
> to do USB 3.0 or 3.1 at only 480Mbps, which is just other spec changes.
>
> Doing 480Mbps/USB 2 over Type C is an option.  But you still need to route
> the video into the type C connector: that's an extra chip unless an SoC
> respin is on the cards.

What extra chip?  Video and USB all come from the SoC, why wouldn't it 
be routed inside the SoC?


> USB 3 burns more power than USB 2.  Most new phones are still USB 2 for
> instance.

Just like the USB before it, 3.1 is fully backward compatible.  The only 
real power hog is the high speed when using it.  If you don't need it, 
use the slower speeds.  If you have use for it, voila, it's there!


> To do type C power requires a redesign of the power system - whether ports
> are 'pushing' or 'pulling' power, and how much to handle of the power
> delivery spec (up to 20V 5A).  You can choose to not do that: be a 5V
> 'puller' only and it's simple, but if you're being a hub it's more complex.

Yeah, the power distribution of the rPi is poorly thought out.  With USB 
3.1 you can do away with the power connector and simplify the power 
distribution.  Very likely a chip will be available to handle all 
aspects of power for small designs like the rPi.  So the current maze of 
power components will be reduced to a small handful with one IC for a 
very low price.


> The bottom line is it's all extra cost.

Bottom line is USB 3.1 with the type C connector is a *big* improvement 
with little or no extra cost for small apps like the rPi.

-- 

Rick

Back to comp.sys.raspberry-pi | Previous | Next — Previous in thread | Next in thread | Find similar | Unroll thread

Thread

rPi and USB 3.1 w/ type C connector rickman <gnuarm@gmail.com> - 2015-10-06 11:02 -0400
  Re: rPi and USB 3.1 w/ type C connector Dom <domafp@blueyonder.co.uk> - 2015-10-06 18:02 +0100
    Re: rPi and USB 3.1 w/ type C connector Jonathan Lane <tidux@faeroes.freeshell.org> - 2015-10-06 20:04 +0000
      Re: rPi and USB 3.1 w/ type C connector rickman <gnuarm@gmail.com> - 2015-10-06 22:40 -0400
        Re: rPi and USB 3.1 w/ type C connector Theo Markettos <theom+news@chiark.greenend.org.uk> - 2015-10-07 11:11 +0100
          Re: rPi and USB 3.1 w/ type C connector rickman <gnuarm@gmail.com> - 2015-10-07 11:47 -0400
            Re: rPi and USB 3.1 w/ type C connector Theo Markettos <theom+news@chiark.greenend.org.uk> - 2015-10-07 19:06 +0100
              Re: rPi and USB 3.1 w/ type C connector rickman <gnuarm@gmail.com> - 2015-10-07 15:35 -0400
                Re: rPi and USB 3.1 w/ type C connector fruit <fruit@invalid.org.uk> - 2015-10-07 21:42 +0100
                Re: rPi and USB 3.1 w/ type C connector rickman <gnuarm@gmail.com> - 2015-10-07 17:27 -0400
                Re: rPi and USB 3.1 w/ type C connector fruit <fruit@invalid.org.uk> - 2015-10-08 07:36 +0100
                Re: rPi and USB 3.1 w/ type C connector Gordon Henderson <gordon+usenet@drogon.net> - 2015-10-08 09:34 +0000
                Re: rPi and USB 3.1 w/ type C connector Rob Morley <nospam@ntlworld.com> - 2015-10-08 19:26 +0100
                Re: rPi and USB 3.1 w/ type C connector rickman <gnuarm@gmail.com> - 2015-10-08 18:40 -0400
                Re: rPi and USB 3.1 w/ type C connector Anssi Saari <as@sci.fi> - 2015-10-11 20:28 +0300
                Re: rPi and USB 3.1 w/ type C connector "A. Dumas" <alexandre@dumas.fr.invalid> - 2015-10-11 20:48 +0200
    Re: rPi and USB 3.1 w/ type C connector rickman <gnuarm@gmail.com> - 2015-10-06 22:47 -0400
  Re: rPi and USB 3.1 w/ type C connector julianmkizner@gmail.com - 2016-11-02 18:08 -0700
    Re: rPi and USB 3.1 w/ type C connector "Kerr Mudd-John" <admin@127.0.0.1> - 2016-11-05 13:01 +0000

csiph-web