After Catalina 10.15.6 update, 3 external (HDMI / VGA / Displayport) displays do not work at the same time
Hello
Usually I work with 3 external displays connected to my MacBook Pro and unfortunately after Catalina 10.15.6 update one display stopped working.
All displays work when I connect them one at a time to the MacBook Pro. When I connect two screens they work correctly the problem is when I connect the 3 screens. No matter the order or combination you make, the screens that work are the first and second that I connect in that order. The last screen connected does not work.
In my case, I use 3 external monitors with the following adapters.
USB-C to HDMI (Apple-branded) https://support.apple.com/es-es/HT207806
USB-C to VGA (Apple-branded) https://support.apple.com/es-cl/HT207807
USB to VGA Converter (RadioShack https://www.radioshack.com/products/radioshack-usb-to-vga-adapter)
After updating Catalina, the USB to VGA (RadioShack) adapter shows the black screen. Apple-branded adapters work properly.
I opened 3 cases with Apple support and they didn't solve my problem. They recommended me to reset SMC, PRAM, start in safe mode, create a new user, etc. but none of these recommendations could solve it.
Thinking that the problem was the USB to VGA converter RadioSHack, I bought 3 USB-C to HDMI adapters (Ditron-branded - made in China) to generate a new test set.
Ditron-branded adapters work ok when I connect them individually. But I can't get 3 external screens to work at the same time as they worked in Catalina 10.15.5
The tests I did are:
1.
Connect the 5 adapters individually (2 apple and 3 ditron) = All work ok
2.
Connect screens 1, 2 and 3 in the following order.
a. USB-C HDMI adapter Apple-branded = Works Ok
b. USB-C VGA adapter Apple-branded = Works OK
c. USB-C HDMI adapter Ditron-branded = Not Working
3.
Connect screens 1, 2 and 3 in the following order.
a. USB-C HDMI adapter Ditron-branded = Works Ok
b. USB-C HDMI adapter Apple-branded = Works Ok
c. USB-C VGA adapter Apple-branded = Not working
4.
Connect screens 1, 2 and 3 in the following order.
a. USB-C HDMI adapter Ditron-branded = Works Ok
b. USB-C VGA adapter Apple-branded = Works Ok
c. USB-C HDMI adapter Apple-branded = Not working
5.
Connect screens 1, 2 and 3 in the following order.
a. USB-C HDMI adapter Ditron-branded = Works Ok
b. USB-C HDMI adapter Ditron-branded = Works Ok
c. USB-C HDMI adapter Ditron-branded = Not Working
I realize that the problem is that Catalina 10.15.6 does not support the use of 3 adapters, regardless of how they are combined. They are ordered by a FIFO (first in first out) system. The first one you connect works supporting a maximum of two.
Several questions came up while testing. For example: if there were a maximum of adapters supported between HDMI and VGA technologies.
When I saw the menu: System Information + Graphics / Displays, I could detect the following:
The Apple-branded USBC HDMI adapter recognizes this as follows: Adapter Type: Apple USB-C Digital AV Adapter
The Apple-branded USBC VGA adapter recognizes this as follows: Adapter Type: Apple USB-C VGA Adapter
The Ditron-branded USBC HDMI adapter recognizes this as follows: Connection Type: Thunderbolt / DisplayPort
In this menu, I could see that Apple-branded adapters recognize them as adapters and Ditron-branded adapters as Thunderbolt / DisplayPort connection type. In this new version of Os Catalina, there will be a limit of adapters that can be combined between Apple USB-C Digital AV Adapter, Apple USB-C VGA Adapter, and Thunderbolt / DisplayPort?
The only test that remains for me to do is get several Apple USB-C Digital AV Adapters and Apple USB-C VGA Adapters and try different combinations but only with Apple-branded adapters.
This last test is very expensive, I hope they solve this problem.
