modstuff
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8GB model - can drive higher current over USB?

Mon Jun 08, 2020 5:45 am

I've got a pretty sweet NAS running on a 4GB with 3 2.5 inch spinning disks hanging off the 3.0 USB ports. Somewhat surprisingly, the system works really well, except at boot, where I need to pull one of the drives before it'll boot up properly.

I read somewhere that the 8GB model does a better job of negotiating higher current rates over USB-C? Is that true? Are folks able to pull higher currents over USB?

PS - I've been astonished that full disk encryption (thanks to the new Chacha cipher and btrfs) has been pretty perform ant - getting reasonable read and write rates. Hoping to share a write up once I have everything working well.

fruitoftheloom
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Re: 8GB model - can drive higher current over USB?

Mon Jun 08, 2020 6:16 am

modstuff wrote:
Mon Jun 08, 2020 5:45 am
I've got a pretty sweet NAS running on a 4GB with 3 2.5 inch spinning disks hanging off the 3.0 USB ports. Somewhat surprisingly, the system works really well, except at boot, where I need to pull one of the drives before it'll boot up properly.

I read somewhere that the 8GB model does a better job of negotiating higher current rates over USB-C? Is that true? Are folks able to pull higher currents over USB?

PS - I've been astonished that full disk encryption (thanks to the new Chacha cipher and btrfs) has been pretty perform ant - getting reasonable read and write rates. Hoping to share a write up once I have everything working well.

Where did you read that anything had changed and was it Official ??


The only change on the RPi 4B 8GB was related to the 8GB Memory Chip:

https://www.raspberrypi.org/blog/8gb-ra ... now-at-75/


There has been a ""fix"" for USB-C using USB Power Delivery Chargers / Cables but that applies to all 4B models.
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Kendek
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Re: 8GB model - can drive higher current over USB?

Mon Jun 08, 2020 6:30 am

modstuff wrote:
Mon Jun 08, 2020 5:45 am
...
I read somewhere that the 8GB model does a better job of negotiating higher current rates over USB-C? Is that true? Are folks able to pull higher currents over USB?

PS - I've been astonished that full disk encryption (thanks to the new Chacha cipher and btrfs) has been pretty perform ant - getting reasonable read and write rates. Hoping to share a write up once I have everything working well.
The max provided current by the Type-A USB ports remains the same. So the total power supplied to all USB ports in aggregate is 1200mA.

The Adiantum performs very well on Pi4, ideal for dm-crypt (LUKS) and fscrypt (ext4). :)
Last edited by Kendek on Mon Jun 08, 2020 6:41 am, edited 1 time in total.

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rpdom
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Re: 8GB model - can drive higher current over USB?

Mon Jun 08, 2020 6:34 am

There have been some changes to the power controllers on the Pi 4B v1.4, but that doesn't affect the USB current at all.

I believe there was a review of the 8GB model that erroneously speculated that the various changes would affect the USB output.
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fruitoftheloom
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Re: 8GB model - can drive higher current over USB?

Mon Jun 08, 2020 6:48 am

rpdom wrote:
Mon Jun 08, 2020 6:34 am
There have been some changes to the power controllers on the Pi 4B v1.4, but that doesn't affect the USB current at all.

I believe there was a review of the 8GB model that erroneously speculated that the various changes would affect the USB output.

Yes that why I asked if whatever the OP ""heard"" was Official as there was some complete crap posted on the WWW as always when ever a "new" model of Raspberry Pi is released.


Bottom line read the Blog, read the comments attached, then ask for clarification in these Forums if still unsure.
Last edited by fruitoftheloom on Mon Jun 08, 2020 8:59 am, edited 1 time in total.
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davidcoton
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Re: 8GB model - can drive higher current over USB?

Mon Jun 08, 2020 8:47 am

fruitoftheloom wrote:
Mon Jun 08, 2020 6:48 am
Bootom line
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modstuff
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Re: 8GB model - can drive higher current over USB?

Mon Jun 08, 2020 11:43 pm

Ah thanks - no change on max current for USB ports.

Do folks have compact workarounds? I've been trying to use a passthrough power USB-C to USB-C hub. The idea was that the 2.5 inch disks would draw directly, and the Raspberry Pi would negotiate some reasonable draw for itself, but with enough room for the disks. Surprisingly this is *less* stable than just directly connecting the Pi to the charger and connecting the drives to USB ports.

Of course a separate powered USB hub would work, but that hardly fits the compact, low profile aesthetic (DC bricks are the very devil, Type-C 4life etc.) I'm going for. Might as well buy a NUC or a NAS at that point :?

trejan
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Re: 8GB model - can drive higher current over USB?

Mon Jun 08, 2020 11:46 pm

modstuff wrote:
Mon Jun 08, 2020 11:43 pm
Ah thanks - no change on max current for USB ports.
Did you by any chance watch ETA PRIME's review of the Pi 4 8GB? He seems to have originated the mistaken idea that the 8GB model had extra power for USB. As noted above, it isn't true. See viewtopic.php?f=63&t=275757 for a previous discussion about this.

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Re: 8GB model - can drive higher current over USB?

Tue Jun 09, 2020 12:13 am

There was a thread in General on this. It was all down to someone's blog that (a) went off half-cocked, and (b) grossly misinterpreted the implications of the change. If anything, by providing more power for the bigger RAM chip, you would expect *less* current to be available to the USB ports. In practice it will be the same 1.2A.

emma1997
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Re: 8GB model - can drive higher current over USB?

Tue Jun 09, 2020 12:35 am

modstuff wrote:
Mon Jun 08, 2020 5:45 am
I've got a pretty sweet NAS running on a 4GB with 3 2.5 inch spinning disks hanging off the 3.0 USB ports. Somewhat surprisingly, the system works really well, except at boot, where I need to pull one of the drives before it'll boot up properly.
This is not specific for Pi4, 8g or otherwise. I've been attaching fthree and even four (when I don't need a kbd/mouse dongle) WD Elements drives. The only trick was to power via GPIO pins with NO wires between converter and Pi. They may click for a few seconds while shuffling power around on startup but quickly settle.

Strangely I had opposite experience regarding hot plug. This causes reboot so I simply just don't do it. IMO it's a good idea to not plug anything in while powered on.

drgeoff
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Re: 8GB model - can drive higher current over USB?

Tue Jun 09, 2020 12:19 pm

modstuff wrote:
Mon Jun 08, 2020 11:43 pm
.. the Raspberry Pi would negotiate some reasonable draw for itself, but with enough room for the disks.
No RPi model released to date has done any "negotiating" with the PSU. They simply try to take what they need.
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