FFXIV & R9 290X Troubles

[Morgwyn]

Nothing - the Process dies and nothing remains in the taskmanager. There are no (other) processes busy.
Only processes of the operating system and the driver of my logitech hardware were up - with standard processor load.

With the Sapphire Radeon HD 7970 the game worked on the same system. I changed to Sapphire Tri-X R9 290X - every other Game I've tried worked fine, only Final Fantasy 14 said "What? THIS graphics-board?! NO, none of my business!" I felt like that
When the Game was merciful and I could run it, there were 1-10fps, for very short moments (one step) 130fps. I overclocked CPU, underclocked CPU, standardclock, TurboCore on, TurboCore off, Cool'n'Quiet on, Cool'n'Quiet off, switched RAM clock from 1866 to 1600 to 1333, I thought perhaps they conflict each other in some way (for FFXIV), but nothing made a difference.


So, and now it gets really bizarre.

In my distress I activated IOMMU in BIOS.
Since then Final Fantasy XIV starts without problems and I have more than 30fps (Revenant's Toll at "PrimeTime") with a R9 290X (deathsman humor). Somewhere out in the sticks of Mor Dhona (i hope this is the correct phrase) up to 150fps and more (Game Graphic-Options at Maximum, Resolution: 1920x1080, fullscreen-windowed, and CPU @ 4,1Ghz = TurboCore on, CPU load was about 48% in Revenant's Toll).
How can that be? I thought IOMMU is for visualization.
Interested in what would happen, i turned off IOMMU again. Game starts, same funereal frames (30+), nothing seems to be changed back to the previous dilemma.
What did IOMMU? Or better, what does FFXIV in the System so as IOMMU makes/made a difference? Now I am totally confused.

A half year ago, on the second PC (win8.1 64bit, also 2 Monitors) I had the problem that only FFXIV crashes the drivers for mouse (roccat) and keyboard (razer synapse) when it get started or switch while playing on the desktop (unnecessary if fullscreen-windowed or fullscreen). And yes, no other Game or Software managed that too at the same time or rather ever.
After many raging moments - I decided to setup win7 (64bit) again
With win7 this issue never took place.
2. PC:
Graphics-Board: GTX 480 at that time (now the Sapphire Radeon HD 7970 from the other system)
CPU: AMD-FX8350, 8x4.00GHz
Mainboard: MSI 990FXA-GD65
RAM: GeIL EVO Corsa 2x4GB, DDR3-1866, CL9-10-9-28
Power-Supply: Coolermaster B700

Some things are going terrible wrong I don't understand I never had such evil troubles with my hardware in any other game.
And it's hard to find tips because everybody has another strange problem with FFXIV.

Sometimes it seems this is the first (one year old) game i know, you should better NOT play with current hardware unless you are a hard- & software specialist.