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USB vs HDMI port for old VGA display connector

Madhatter32

Madhatter32

macrumors 68000
Original poster
Apr 17, 2020
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Does it make a difference on how to connect an old external VGA display to a macbook pro m4? Is it more advantageous to use the USB-C or the HDMI port with a VGA adapter? Thanks!
 
Not sure if this detail will make a difference but what model monitor is it?

If it were me and everything is equal between the two choices I'd probably go with HDMI and leave the other port open for something else.
 
BrianBaughn said:
Not sure if this detail will make a difference but what model monitor is it?

If it were me and everything is equal between the two choices I'd probably go with HDMI and leave the other port open for something else.
Click to expand...
It's a very old and cheap Acer but can still display charts just fine. With the new laptop I just need to get an adapter to keep it running. Thanks.
 
VGA is low bandwidth. It's difficult to find an adapter that can do 350 MHz. GPUs that supported VGA could do 400 MHz or more.
HDMI 2.0 is limited to 600 MHz. HDMI 1.4 is limited to 340 MHz. HDMI 1.0 is limited to 165 MHz.
DisplayPort 1.2 is limited to 720 MHz. DisplayPort 1.1 is limited to 360 MHz.

You probably want to use the HDMI port to keep the USB-C ports free for high bandwidth data or video.

The Plugable USB C to VGA Adapter (usbc-vga) can do 330 MHz.
https://support.plugable.com/t/high-speed-vga-from-displayport-1-2-or-hdmi-2-0/8816
 
joevt said:
VGA is low bandwidth. It's difficult to find an adapter that can do 350 MHz. GPUs that supported VGA could do 400 MHz or more.
HDMI 2.0 is limited to 600 MHz. HDMI 1.4 is limited to 340 MHz. HDMI 1.0 is limited to 165 MHz.
DisplayPort 1.2 is limited to 720 MHz. DisplayPort 1.1 is limited to 360 MHz.

You probably want to use the HDMI port to keep the USB-C ports free for high bandwidth data or video.

The Plugable USB C to VGA Adapter (usbc-vga) can do 330 MHz.
https://support.plugable.com/t/high-speed-vga-from-displayport-1-2-or-hdmi-2-0/8816
Click to expand...
Thanks. I'm now having trouble finding an HDMI to VGA adapter that has enough power to use with a new MBP. Apple makes to difficult to use old technology.
 
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BrianBaughn said:
What "power" is it that's lacking in the adapters you're seeing?
Click to expand...
Many listings state that the Mac has a "lower power HDMI port" and say something like the following or similar:

COMPATIBILITY: Connects a computer, laptop, Xbox, Roku, or other device with HDMI port to a TV, monitor, projector, or other device with VGA port. For laptops, works with Windows PCs like Lenovo Yoga / ThinkPad, HP Elite, Dell XPS, Microsoft Surface, Razer, LG, Acer laptops and more. NOT compatible for devices with low-power HDMI ports like Blu-ray player, PS4, PS5, Apple MacBook Pro, Mac mini, Apple TV. Do not use any converter/adapter between the laptop and cable

https://www.amazon.com/Gold-Plated-...8-1-spons&sp_csd=d2lkZ2V0TmFtZT1zcF9hdGY&th=1

Amazon Basics HDMI (Source) to VGA (Display) Cable (NOT Bidirectional), Gold-Plated, 6 feet, Black

An Amazon Brand
www.amazon.com

I'm obviously not an expert on this stuff but I do want to avoid getting something that will not work if I can help it. Thanks.
 
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I guess you just need to determine what your requirements are for cable length, if you need male or female VGA connection, what your desired resolution is on the monitor that you didn't specify and so on.

Just narrow it down to adapter cables that meet those requirements and then search the reviews for success stories regarding Apple Silicon powered MacBook Pros.
 
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Fishrrman said:
I just looked on amazon and there are all kinds of HDMI-to-VGA adapters.

I reckon just about any one of these is going to work for you...

Amazon.com: HDMI-to-VGA Adapters - HDMI-to-VGA Adapters / Computer Cable Adapters: Electronics

Shop a wide selection of HDMI-to-VGA Adapters at Amazon.com. Free shipping and free returns on eligible items.
www.amazon.com
Click to expand...
Thanks. I have done that search and found that with regard to the HDMI port adapter many will not work because they say that the MBP has a "lower power HDMI port" and will not work. For example:

COMPATIBILITY: Connects a computer, laptop, Xbox, Roku, or other device with HDMI port to a TV, monitor, projector, or other device with VGA port. For laptops, works with Windows PCs like Lenovo Yoga / ThinkPad, HP Elite, Dell XPS, Microsoft Surface, Razer, LG, Acer laptops and more. NOT compatible for devices with low-power HDMI ports like Blu-ray player, PS4, PS5, Apple MacBook Pro, Mac mini, Apple TV. Do not use any converter/adapter between the laptop and cable

I do think I have found one though -- it connects to the both the HDMI port and the USB-C (in order to draw power). Otherwise, I guess I need to start looking at the USB-C to VGA adapters to avoid any problems. Thanks.
 
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I have a USB C docking station that has a VGA connection. You can get these for pretty cheap. You can connect all your devices and monitors to the docking station.
 
Madhatter32 said:
Many listings state that the Mac has a "lower power HDMI port" and say something like the following or similar:

COMPATIBILITY: Connects a computer, laptop, Xbox, Roku, or other device with HDMI port to a TV, monitor, projector, or other device with VGA port. For laptops, works with Windows PCs like Lenovo Yoga / ThinkPad, HP Elite, Dell XPS, Microsoft Surface, Razer, LG, Acer laptops and more. NOT compatible for devices with low-power HDMI ports like Blu-ray player, PS4, PS5, Apple MacBook Pro, Mac mini, Apple TV. Do not use any converter/adapter between the laptop and cable
...URL]

I'm obviously not an expert on this stuff but I do want to avoid getting something that will not work if I can help it. Thanks.
Click to expand...
HDMI and VGA signalling are radically different. It takes some "computing" effort to convert HDMI into VGA. This requires electrical power (voltage x amperage) to do the conversion and to generate the output signals. Many HDMI ports, including many (most/all??) ports on Apple devices, do not provide adequate electrical power. For a converter to work reliably with such host devices it needs an external source of power. This is usually done via a third connection to either a USB-A or USB-C port, either on the host device, a powered hub, or a AC power adapter. The adapter I bought some years ago to do this with my wife's MacBook worked fine, but did require the external power.
 
dwig said:
HDMI and VGA signalling are radically different. It takes some "computing" effort to convert HDMI into VGA. This requires electrical power (voltage x amperage) to do the conversion and to generate the output signals. Many HDMI ports, including many (most/all??) ports on Apple devices, do not provide adequate electrical power. For a converter to work reliably with such host devices it needs an external source of power. This is usually done via a third connection to either a USB-A or USB-C port, either on the host device, a powered hub, or a AC power adapter. The adapter I bought some years ago to do this with my wife's MacBook worked fine, but did require the external power.
Click to expand...
Good information. I guess it would make more sense to just go with a USB-C to VGA adapter then. Thanks.
 
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