TCC Mode only offers CUDA (and in some cases OPENCL) and does not use the windows driver mode. For CUDA, it can have some speed benefits, since the windows-overhead is not present…
But if you want to do anything “windows related”, you have to set it to WDDM Mode
So it´s perfectly normal that it doesn`t show up in windows, if set to TCC mode…
Some Cards are set to default to TCC (Compute cards like Tesla), others are default to WDDM (like Quadros or Geforce).
As long as the chip on the card is the same as one present on a consumer or worksation (Quadro) Card, chances of being able to use them in windows in WDDM Mode are 99,9%
I´ve tested (and all worked in WDDM Mode - i`ll only list those which make sense in VEAI, those not supported anymore or simply too slow I´ll leave out - like older fermi ones which used to work, too…)
Tesla K20(x/c, etc…)
Tesla K80 (here is one example where my proposition will be important - 2 Chips on the card…)
Grid K1 (ok, way too slow, but works…)
Chips like GA100 (Ampere Cluster Card for Compute Clusters have special variants with NO other circuits/firmware than CUDA/OPENCL - those can`t be set to WDDM (hardware does not support it).
Looking at the cards “normal people” will get theyr hands on - chances that a headless GPU will work just fine when set to WDDM are VERY high.
The diffiulty simply is, that many people don`t know how to set them up, have the wrong motherboard (lacking "abovce 4G decoding for bigger cards,), set UEFI wrong, or simply don´t know about how to set them to WDDM… The fact that most guides on the internet are either - old / wrong / too complicated doesn´t add to the impression, that this is “way too complicated” to get it running - the cooling solution also doesn´t “help”…
Aside from headless GPUs - my proposition also applies to people having more than two Chips in the system. Of course, everone only using one GPU doesn´t care about that - but I know enough people at offices having three quadros in they workstation for comutational stuff - one being a small card only to feed the displays, two being quite powerful Turing Quadros - which can´t be set to good use in VEAI because they can´t be selected (only together with the smaller card)…