If you get a good picture, then I think you’re fine and I wouldn’t bother overthinking it.
This is all digital data. If the signal comes across clean enough for the monitor to correctly distinguish the ones and zeros, then that’s all you need. If not, then you may see a messed up image (sparkling pixels or other artifacts) or a blank screen. In which case, the cable simply “doesn’t work” for your computer and display.
There are technically four different kinds of HDMI cables. The higher grades support more bandwidth than the lower grades, but what you actually need depends greatly on how much bandwidth your specific usage (e.g. resolution, color depth, etc.) requires, not the HDMI version numbers that your products may document:
- Standard, aka “category 1”, should support at least 74.25 MHz. This corresponds to 4.95 Gbit/s of data and should support all HDMI features up to version 1.2. This includes 1080p resolution at 60 Hz and 1440p at 30 Hz refresh.
- High speed, aka “category 2”, should support at least 340 MHz. This corresponds to 10.2 Gbit/s of data and should support all HDMI fetures up to version 1.4. This includes 1440p at 75 Hz and 4K at 30 Hz.
- Premium high speed is also “category 2”, but it should support at least 18 Gbit/s of data and should support all HDMI 2.0 features. This includes 4K at 60 Hz and 5K at 30 Hz.
- Ultra high speed, aka “category 3” or “48G” should support at least 48 Gbit/s of data and should support all HDMI 2.1 features. This includes 4K at 120 Hz, 5K at 60 Hz and 8K at 30 Hz.
But it is also important to note that:
- The standards are the minimum. You might be able to get a solid 4K 60Hz image using non-premium high speed cable or even a standard cable. But there will be no guarantee.
- None of the above is guaranteed unless the cable is certified. There are lots of uncertified cables which may or may not meet the standards with which they claim to comply.
- Cables that come with displays for free are often not certified. You would like to think that they can handle whatever the bundled display supports, but there’s no guarantee.
- Length matters. Bulk cable that passes certification tests at some category for a 3m cable may fail those same tests for a 6m cable. Which is why bulk cable is never certified - only finished cables with connectors. It also means that if you try to extend a cable, the result might not work.
In short:
- If you’re buying a cable, take a bit of time to determine the amount of bandwidth you will require and make sure you buy a cable certified to handle that much data.
- The Wikipedia table for frequency limits is a good starting place.
- Or if this all sounds like too much, then just buy a certified Ultra High Speed (“48G”) cable. It will work with anything you throw at it, but it might cost a little more than you technically need to spend, if your usage is within the capabilities of a lower-grade cable.
- If you’re already got a cable (e.g. bundled with your display), give it a try. If you’ve got a solid high quality image, then you’re good to go. If there are problems, then don’t assume there’s anything wrong with your computer or display (in the absence of any other symptoms, of course) - just go get a better cable.
You might find this video of interest:
