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I have RPi 3B+ connected to exactly the same router as my PC (wired!).

I have installed Speedtest.net client using this guide. When executing speedtest-cli --simple, I am getting nearly exactly twenty times worse speed results than on my PC:

enter image description here

This isn't "today's a bad day" because I am observing such deviations for days, if not weeks so far (anyway, as long as I am measuring this).

Can someone explain me this quite odd behaviour?

EDIT: Both PC and RPi are wire-connected (so no Wi-Fi related issues are asked here).

EDIT: Someone could think that this is a question about 3rd party software (speedtest-cli) and thus off-topic. It is not. The very similar results (very low download speed in compare to overall network speed) I am getting in many other places and when fetching data from many other sources (i.e. apt upgrade for updating packages and wget for fetching files from various sources). This question is about RPi hardware (RJ45 port and chip that controls it) and its quality, performance or speed.

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    you wired or wireless on the pi? if wireless, 2GHz or 5Ghz band - my B+ is about 8Mbit on 2Ghz, and 78Mbit on 5Ghz and 98MBit on wired (100MBit is the max for me though) Jun 30 at 2:09
  • Sorry for not mentioning this earlier. Please, see the edited question. Both RPi and PC are connected via cable to the same wall-router.
    – trejder
    Jun 30 at 12:10
  • A more legitimate (as in, less prone to factors that have nothing to do with the pi) test would be demonstrating that two pc's (or other non-pi devices) on your WLAN can transfer data between themselves significantly faster than between the pi and one of the pc's, using the same application level protocol (eg., http, ssh, etc; an even better test would be one which use no application level protocol, but I think the only way to do that is code it yourself, speedtest-cli presumably still uses http).
    – goldilocks
    Jul 4 at 14:02
  • I agree with you that the deeper into OSI model we go, the more reliable results we'll get. But, on the other hand, even top level should be enough. At high (business) level: If all tested services on RPi are very slow (15-20x slower) while in the same moment of time and for a PC connected to the same cable router, all services are very fast. And if a service fetching data from the same source (speedtest.net) through the same protocol (HTTP) has so different results on both devices then I think that these are still quite legitimate tests. Plus: a very good answer below -- poor hardware.
    – trejder
    Jul 4 at 14:57
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First, even ignoring possible issues with wifi vs. wired networks, the pi 3's network can't quite provide full bandwidth to a 1G network, although for an external connection, this might not matter as it is likely slower than what the pi can provide.

The pi has a slower cpu with less bus bandwidth and fewer I/O lines than pc's that are contemporary with the pi, and if the speed test is running on the pi cpu, this could affect it, especially if the speed test is written in a language that is slow on the pi.

The bus between the pi cpu and the network interface is shared by other devices (like possibly usb, serial, others, possibly even in the same chip), and if those devices are active, it can slow the network down further.

These problems are typical for inexpensive small form factor single board computers similar to the pi, with differing levels of issues with shared buses, shared I/O on the same chip, and lack of hardware offloading of I/O.

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  • Sorry for not mentioning this earlier. Please, see the edited question. Both RPi and PC are connected via cable to the same wall-router. Please, see if this changes anything in your answer. Thank you.
    – trejder
    Jun 30 at 12:10
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I think the "speedtest-cli" you are using (installed via package managers) might be broken or might have bugs.

Why do not you download "Speedtest CLI" from its official website?

Near the bottom of https://www.speedtest.net/apps/cli

enter image description here

I believe you can find the architecture of your system with this command: dpkg --print-architecture

UPDATE #1 For those who are not sure how to download files from a shell, here is an example: wget https://url_of_the_file_you_want_to_download

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  • The website, you're pointing to, says about executing sudo apt-get install speedtest in the console. This is exactly the same command that I used, so I believe that my speedtest-cli is the same and is not broken.
    – trejder
    Jul 1 at 19:49
  • Did you check out the download section seen on the screenshot I attached?
    – vaha
    Jul 1 at 20:28
  • No, because these requires a graphical interface for RPi while I am on bare console-only Linux for RaspberryPi and cannot install any graphical interface app or anything requiring window manager. I can only install anything from console, nothing else.
    – trejder
    Jul 2 at 8:01
  • I do not think you need a GUI for downloading files. Check out the update in my answer!
    – vaha
    Jul 3 at 17:14

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