negativeions369
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I don't understand the point of still using USB 2.0

Mon Jun 24, 2019 4:41 pm

If USB 3 is backward compatible, why does anyone in the world bother with USB 2? Shouldn't all USB ports just be USB 3?

webbsmurfen123
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Re: I don't understand the point of still using USB 2.0

Mon Jun 24, 2019 5:11 pm

Well i dont see a reason for a Raspberry Pi to do and handle more than 480Mb/sec (or 60MB/sec) transfers. Nor do i see the reason you need a Raspberry Pi to handle the full speed of USB3 (5Gb/sec or 640MB/sec). Whats the idea to build something that have a function you never going to use to its fully potential anyway

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jbeale
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Re: I don't understand the point of still using USB 2.0

Mon Jun 24, 2019 5:35 pm

The Pi3 doesn't have a USB3 capable hardware module in the SoC. The newly announced Pi4 does have USB3 hardware, but the reason it has only 2 USB3 rather than 4 was described as wiring limitations on the PCB. USB2 ports only need two data lines in addition to two power lines, whereas USB3 needs six data lines in addition to power and it didn't fit in the existing form factor. With the 10x higher frequencies used, I am sure the the line length matching and impedance on USB3 signal lines is more critical as well, and potential RFI/EMC issues. Not everyone would be happy with more USB3 ports if it means your wifi doesn't work anymore.

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RichardUK
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Re: I don't understand the point of still using USB 2.0

Mon Jun 24, 2019 5:40 pm

Yes I was wondering why it had only 2 USB 3.0. I think your suggestions are spot on.

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mahjongg
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Re: I don't understand the point of still using USB 2.0

Mon Jun 24, 2019 6:17 pm

Most often two USB ports are only used to connect a keyboard and a mouse anyway.

k-pi
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Re: I don't understand the point of still using USB 2.0

Mon Jun 24, 2019 6:23 pm

USB2 for keyboard & mouse - USB3 for data transfers. 8-)

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FTrevorGowen
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Re: I don't understand the point of still using USB 2.0

Mon Jun 24, 2019 6:48 pm

k-pi wrote:
Mon Jun 24, 2019 6:23 pm
USB2 for keyboard & mouse - USB3 for data transfers. 8-)
+1
I've found using a USB3 flash drive** and USB3 card reader**** very good for writing/transferring/cloning O.S. images
Trev.
** http://www.cpmspectrepi.uk/raspberry_pi ... lash_Drive
**** http://www.cpmspectrepi.uk/raspberry_pi ... oSD_Reader
Still running Raspbian Jessie on some older Pi's (an A, B1, B2, B+, P2B, 3xP0, P0W) but Stretch on my 2xP3A+, P3B+, P3B, B+, A+ and a B2. See: https://www.cpmspectrepi.uk/raspberry_pi/raspiidx.htm

gkaiseril
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Re: I don't understand the point of still using USB 2.0

Mon Jun 24, 2019 7:06 pm

Compatible might not mean everything is compatible. USB 3.0 may be backward compatible with the USB 2.0 standard, but there could easily be a device that runs on a USB 2.0 port that is not compatible with the USB 2.0 standard. Since the Pi is a learning device and there are many users building custom circuits it is possible that some might not have fully followed the standard. This might just be a CYA and as noted keyboards and mice are low speed devices that can be used by the USB 2.0 ports without impacting pervformance.
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Re: I don't understand the point of still using USB 2.0

Mon Jun 24, 2019 7:17 pm

A number of my archive drives are in USB2 enclosures and I’ve no plans to spend money on this data till I migrate them to larger, faster, newer disks.

For me the older drives will go in the USB2 ports and faster / more up to date data can go in the USB3 ports and as the Pi boxes are normally headless this mix fits fine with my use case.
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FTrevorGowen
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Re: I don't understand the point of still using USB 2.0

Mon Jun 24, 2019 7:33 pm

gkaiseril wrote:
Mon Jun 24, 2019 7:06 pm
Compatible might not mean everything is compatible. USB 3.0 may be backward compatible with the USB 2.0 standard ...
Things may have changed but, AIUI, USB 1.0, 2.0. 3.0 ... has never been a "standard" (in the ISO sense) but rather (and certainly originally) an "agreed specification" between a number (consortium) of (chip) manufacturers. So, yes, there are quite a few devices "out there" (usually not made by the "consortium") that don't quite meet the USB 2.0 specs. (Example: quite a few USB2.0 hubs which "back-power" when they "shouldn't" ). Thankfully there's not as much deviation as there became between devices "conforming to" the RS232 serial comns'. spec's ;)
Trev.
Still running Raspbian Jessie on some older Pi's (an A, B1, B2, B+, P2B, 3xP0, P0W) but Stretch on my 2xP3A+, P3B+, P3B, B+, A+ and a B2. See: https://www.cpmspectrepi.uk/raspberry_pi/raspiidx.htm

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HawaiianPi
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Re: I don't understand the point of still using USB 2.0

Mon Jun 24, 2019 7:34 pm

In addition to what was stated above, USB 3.0 is not always backwards compatible. I've experienced issues on USB 3.0 ports with some USB 2.0 devices. For example, flashing a custom ROM into a mobile device has failed for me a number of times on different devices, yet it always works on USB 2.0 ports. Admittedly, that's not a common use case, but I like to have at least one true USB 2.0 port on my computers.

The 2x2 arrangement on the Pi 4B is fine with me.
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Re: I don't understand the point of still using USB 2.0

Mon Jun 24, 2019 8:35 pm

mahjongg wrote:
Mon Jun 24, 2019 6:17 pm
Most often two USB ports are only used to connect a keyboard and a mouse anyway.
Ah! But if you use the Official RPF keyboard and plug the mouse into the keyboard's hub, you only need 1 USB 2 port, leaving the other for any medium speed device you might want to attach.

chwe
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Re: I don't understand the point of still using USB 2.0

Tue Jun 25, 2019 12:05 am

W. H. Heydt wrote:
Mon Jun 24, 2019 8:35 pm
mahjongg wrote:
Mon Jun 24, 2019 6:17 pm
Most often two USB ports are only used to connect a keyboard and a mouse anyway.
Ah! But if you use the Official RPF keyboard and plug the mouse into the keyboard's hub, you only need 1 USB 2 port, leaving the other for any medium speed device you might want to attach.
that's a big if.. :lol: Likely the majority of people have some old keyboards and an unused usb mouse they might to reuse.
webbsmurfen123 wrote:
Mon Jun 24, 2019 5:11 pm
Well i dont see a reason for a Raspberry Pi to do and handle more than 480Mb/sec (or 60MB/sec) transfers. Nor do i see the reason you need a Raspberry Pi to handle the full speed of USB3 (5Gb/sec or 640MB/sec). Whats the idea to build something that have a function you never going to use to its fully potential anyway
well, you might not see it, others might see it. I didn't saw a reason to buy a RPi3b+ cause it was IMO broken by design. I don't have the numbers but likely millions of people saw it different and bought one. Maybe the 3b+ was for their purpose the perfect SBC, only cause you (and for the 3b+ I) didn't saw a reason to have it doesn't mean there's no reason to have it. :lol:
negativeions369 wrote:
Mon Jun 24, 2019 4:41 pm
If USB 3 is backward compatible, why does anyone in the world bother with USB 2? Shouldn't all USB ports just be USB 3?
Maybe BOM costs? 4 good quality USB3 ports are for sure more expensive than the 2x2 mix (and a crappy USB3 connector is just a nightmare). Routing on the PCB might be tricky as well (who knows, I'm not an expert here but the fact they swapped USB and RJ45 is an indicator that routing wasn't as easy). On the first lock the balance between price and what you get looks a way better than the last two iterations (I still don't care about HDMI, my stuff runs headless (once again, different people different use-cases), but GbE over RGMII separate from the whole USB stuff was a good pick, finally GbE landed on the RPi not only 'by electrical characteristics' - sorry @jamesh, I had to comment on that :mrgreen:). For me, the most interesting part is the increased horse power with 4xA72 combined with GbE.

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