Apple iMac 27-Inch (2019) running bootcamp has slow internet speed

There is a newer version of this driver (101.10.152.5). Can you download the latest Windows Support package using Bootcamp Assistant -> Action -> Download and check Bootcamp.xml for the provided version?

Also, since you were/are able to get higher speeds, the driver may be attaching to a slower radio (.11n) instead of the faster one (.11ac). In some cases .11ax Access Points also cause issues.

I assume this is your router/gateway - Univision_A814. Do you have access to the Management User Interface of this device? If yes, we should look at the configuration. It should have the ability to change the channels. Channels 2, 6 and 11 are normally used for 2.4GHz radio, which is prone to interference. If you notice, the connection from your macOS side uses channel 36 at 80 MHz, not channel 11. This seems to be the root cause of your slow speed issue.

If you do not have access to the Management UI, you may have to ask your ISP to set the channel to Auto and test.

Tsenguun___ wrote:

I think I've found the cause: after I downloaded the game "VALORANT", it required restart, and after doing so, the internet speed fell.

Your iMac is switching between two different networks or two different radios.

Also, a temporary workaround: by booting into macos and booting back into windows.

Should I run the link test while in Windows?

You should run it in Windows. Also, next time you boot into macOS, Option+click on the WiFi icon, and take a screen shot using Command+Opt+4. It will look similar to the following.

I will post sections of the configuration I have, to avoid confusion.

The Profile used to connect to this network is

The Profile contents are

The Radio the WLAN adapter sees are

Let me compare the two for any anomalies that I can spot.

One noticeable item is that the Tx Rate is low in your report. Can you change the Access Point to a channel other than 11?

  Radio type             : 802.11n

    Authentication         : WPA2-Personal

    Cipher                 : CCMP

    Connection mode        : Auto Connect

    Channel                : 11

    Receive rate (Mbps)    : 1300

    Transmit rate (Mbps)   : 57.5

    Signal                 : 83%

In Windows Device Manager, if you click on Update Driver -> Have Disk and point to the BroadcomWireless directories, are you offered a newer version? Do not update the driver. We need check available versions. You can also check the .INF files, if that is an easier method for you.

Your 2019 iMac is capable of more than 130 Mbps Tx Rate. Can you look at https://support.microsoft.com/en-us/windows/analyze-the-wireless-network-report-76da0daa-1db2-6049-d154-7bb679eb03ed and check what you see from the Windows side?

Can you post he output of

NetSh WLAN Show All

You may want to copy/paste a text version, instead of screen shots, because it can be a fairly long output.

Macs on macOS have the ability to act as network sniffers. Do you have a portable Mac? If yes, see the sniffers section in If your Mac doesn't connect to the Internet over Wi-Fi - Apple Support. Given that the iMac sees and connects to .11ac on the macOS side, you should see the RSSI/SNR and the negotiation.

We can also use Wireshark to see the exchanges between the iMac in Windows and your AP.

Can you post the PID/VID of the Wireless adapter? Here is an example.

If macOS driver can connect via .11ac, the Windows one can, too. If you can create a System Restore point, we can try to update the driver to .5 and see if it makes any difference.

Can you take a look at https://support.microsoft.com/en-us/windows/analyze-the-wireless-network-report-76da0daa-1db2-6049-d154-7bb679eb03ed?

We should run this when you have good speed results and then again when they are bad, and compare.

From your output...

Radio types supported : 802.11a 802.11n 802.11g 802.11b

This is incorrect. You should also have 802.11ac. .11a is close. Your Radio connection shows 802.11n, which is causing you to slow down.

  Name                   : Wi-Fi

    Description            : Broadcom 802.11ac Network Adapter

    GUID                   : 405da8e0-2102-42b9-8cde-e9c2c72fe870

    Physical address       : a4:83:e7:40:91:12

    State                  : connected

    SSID                   : Univision_A814

    BSSID                  : 84:46:fe:d9:a8:24

    Network type           : Infrastructure

    Radio type             : 802.11n

    Authentication         : WPA2-Personal

    Cipher                 : CCMP

    Connection mode        : Auto Connect

    Channel                : 11

    Receive rate (Mbps)    : 1300

    Transmit rate (Mbps)   : 57.5

    Signal                 : 83%

    Profile                : Univision_A814

How far away is your iMac from the router/gateway? Are there any obstructions in the path? In most cases, a line-of-sight path is the most efficient for wifi.