Not sure if I can install pmdg into both sims at the same time. I did suffer from random ctd so gone back to 4.5 as for me it's way more stable currently. however that's after a full 5.1 full reinstall. I am now able to get 20-30fps locked at 30. single figure FPS anywhere in default or Orbx scenery in any aircraft. For P3D the same configuration has been reported multiple times to run amazingly fluent (at least when the CPU is delidded and overclocked to 5GHz) but most of those test reports appear to be using a quite naked installation with barely any scenery or complex aircraft addons. Everything apart from P3D runs so fluent that I still don't see any reason to upgrade that system in the next years.

Should be running P3D great in theory but it isn't. Quick summary of my system: i7-4790K 4.0GHz/4.4 Turbo, not overclocked, 32GB RAM, GeForce 1070 (not Ti) with 8GB VRAM, sim running from MLC-SSD. I hoped that P3D v5 would maybe finally optimize that but it seems that has not happened. I've spent a lot of money on hardware and my even more valuable spare time trying to get just a few more frames out of that sim but it appears there's just some hardcoded barrier in P3Dv4 that I cannot get past, it's most-likely the unflexible 1990s multithreading-on-a-single-CPU-thread scheduler that's uselessly keeping 60% of CPU free for texture loading etc. High FPS on P3D is like a holy grail and I know there are systems running full addon setups which manage >20FPS. I've started flightsim 6 years ago on XP10, switched to P3Dv3 for the graphics and airliners, v4 for stability, now I'm back on XP11 since last year as it feels so more alive having 25-30 FPS reliably and not just while on cruise level. I would wish to be able to use all the expensive scenery and deep study-level addons I bought for P3D but all the low-FPS stutter completely breaks immersion and is highly annoying/inaccurate while hand flying and even during taxi, it's just no fun. Last year I managed to improve the FPS (what I just wrote is already maxed out on my system) and I still don't understand why P3D 4.5 just does not use the resources my system offers - it is happily stuttering although the system appears almost idle at just 30-40% CPU (each core, not just total) and 35% GPU load and with plenty memory free on both RAM and VRAM. Other aircraft such as the Majestic Dash 8 are much better, as is less dense scenery but I would really love to fly PMDG aircraft over Central Europe. Other areas are a bit more manageable such as Aerosoft Cologne with Orbx GES which peaks at around 18 FPS.

Aerosoft scenery gives ~13-15 FPS while parked at the gate, Gaya manages to go even lower with 8-12 FPS.

Example for worst performance on my system: Loading up Berlin-Tegel in a PMDG 738 NGXu and full Orbx scenery incl.

Pmdg 737 ngx prepar3d install