I carry a box full of video adapters with me because I see this CONSTANTLY with people buying new monitors that lack whatever port on them is directly compatible with whatever port is on the video card.
Let me explain the nitty-gritty of these adapters. DisplayPort was designed for use with passive (chipless) DP to HDMI cables and cable adapters. What happens is when you plug an HDMI cable into an adapter and the adapter into a DP, the chip in the video card senses that you are using an adapter and chances the signal from DP to HDMI or from DP to DVI depending on what adapter in use. This is referred to as multi-mode or DP++ technology. This is why you generally can't go from DVI output "backwards" into HDMI input on the monitor. An HDMI port on a video card by contrast has no logic, and if you are going to use an HDMI output on the video card to DP input on the monitor your adapter cannot be passive it must be active with a chip in it. The same thing exists if you are going from DP or HDMI on the graphics card to VGA input on the monitor. The biggest problem with "active" adapters is they usually attempt to steal power from the HDMI output or DP output on the card. There is VERY LITTLE power available from these ports and it can often screw things up. Most of the time the passive adapters work OK but what what screws those up are cheaper video cards that don't properly handle DP++ or shoddy contacts. The more adapters you plug in between the video card and the monitor the more opportunity you have to poor contacts that don't transmit the signals properly. Going from HDMI to DP or VGA or DVI is the biggest opportunity for screw up. Generally going from DP to HDMI is not a problem UNLESS the adapter itself has bad contacts. I have a couple of those video adapters - look perfect, even looking inside with a magnifying glass the contacts look perfect, the connectors solidly lock, no evidence of bending strain on the cord - yet no signal whatsoever that goes through. Not all passive adapters are the same, though. I have had to play musical chairs with Display Port to DVI adapters, where one works OK with one combo, a different one does not or is intermittent. This may be because DP++ can't properly sense an adapter is in use because they have done something with tying off the unused signal pins wrong. In general any old crappy HDMI cable will work on a short 4 foot run. But, on a longer run from say a projector to a PC go to PCH Cables in Hillsboro and tell him what you are doing and get the most expensive triple insulated HDMI cable you can get. I had one customer, an engineering firm full of DIYers who had gone through THREE 25 foot HDMI cables from their overhead projector to their PC and had intermittent problems with all cables and were convinced that the projector was messed up, they had also tried 2 different PCs assuming the HDMI port on the PC might have been the problem. I replaced the HDMI cable with one of the high quality 25 foot PCH Cables cable and the setup ran perfectly. None of them could believe it and kept looking at the HDMI cables they bought and muttering. I told them just because you spent a lot of money on a cable does not mean it's any good. Very likely a high quality DP to HDMI cable instead of a DP to HDMI adapter then HDMI to HDMI cable would fix the issue as well but what I always tell people buying monitors is if you are going to use it on a computer with a DP port output on a video card, get a monitor with a DP input. The scuttlebutt I heard was that MPAA extracts a license fee for HDMI which is why the computer industry created DP. I can also tell you that the Raspberry Pi outputs HDMI and if you use an active adapter on it (to go to VGA) then it will increase the power draw and if the Pis' power supply is marginal it will screw the Pi up. If you even boot a Pi with a monitor connected it turns on the Pis video chip and increases power draw so you have to watch that with marginal 5v supplies. Ted -----Original Message----- From: PLUG <plug-boun...@pdxlinux.org> On Behalf Of Rich Shepard Sent: Tuesday, March 21, 2023 7:24 AM To: Portland Linux/Unix Group <plug@pdxlinux.org> Subject: Re: [PLUG] New monitor issues [RESOLVED] On Tue, 21 Mar 2023, Rich Shepard wrote: > I'll replace the WX-2100 with the RX-550. Instead, I bought a Radeon RX-850 (four times more memory) and I'll buy a high-speed HDMI cable to replace the Amazon Basic one. Never considered that HDMI cables had different qualities. Thanks all, Rich
