GTX 1070 getting 25 FPS in GTA 5 benchmark at Normal settings

[Dogwood11]

Fallout 4 and Shadow of a Mordor run beautifully at highest graphic settings (SOM benchmarks around 120 FPS) but Grand Theft Auto V lags terribly at GeForce Experience-optimized settings, the game's mid-tier defaults and manually set low levels. When I run benchmark from menu, I get 25 FPS whether I'm in high or low settings.

I've explored just about every solution Google could turn up here and Reddit.

My system (just completed first-time PC build):

• 
  CPU: Intel Core i5-6500 3.2GHz Quad-Core Processor with stock cooler
  Motherboard: Gigabyte GA-Z170X-Gaming 5 ATX LGA1151 Motherboard
  Memory: G.Skill Ripjaws V Series 16GB (2 x 8GB) DDR4-2400 Memory
  Storage: Samsung 850 EVO-Series 250GB 2.5" Solid State Drive
  Storage: Western Digital Caviar Blue 1TB 3.5" 7200RPM Internal Hard Drive
  Video Card: EVGA GeForce GTX 1070 8GB
  Case: Corsair SPEC-03 White ATX Mid Tower Case
  Power Supply: Corsair CXM 650W 80+ Bronze Certified Semi-Modular ATX Power Supply
  Operating System: Microsoft Windows 10 Home Full - USB 32/64-bit
  Monitor: HE 2711X 1080P 60Hz

I've tried the following:

• 
  ■ Updated GPU driver
  ■ Uninstalled and reinstalled updated GPU driver
  ■ Checked for CPU driver update
  ■ Confirmed that GPU, not the CPU, is handling graphics
  ■ Confirmed all 16GB RAM is correctly slotted
  ■ Confirmed GPU is in first PCI slot
  ■ Tried Vsync on and Vsync off in graphics settings
  ■ Checked CPU clock speed in BIOS (100mhz at 32 multiple)
  ■ Used GeForce Experience to optimize settings
  ■ Opened device manager to confirm PC is recognizing all my installed components.

The 1070 is connected to the monitor via HDMI. I've noticed that graphics settings tend to default to 50hz or 59Hz even though my monitor is rated 60Hz.

I've also read that the CPU could be throttling itself if cooling is inadequate. Stock cooler appears to be running without issue. The machine is very quiet – the towers 3-pin fans run at a constant, quiet velocity the

Could the 1070 have an undocumented incompatibility with GTA V?

Could running it off an HDD be a factor?

I downloaded the game from my brother's Steam account. Could that be an issue?

All my games are saved to a folder I created on the D: drive instead of the default C: drive location Windows 10 created.

 

[Dogwood11]

SOLVED? Although I could swear I tried it with Vsync on and Vsync off, after noticing Nvida's Geforce Experience app set Vsync to "half" when optimizing settings, I loaded the game, manually set Vsync to "off" and lo and behold got 60-100+ FPS in the benchmark demo.

Oh, I also started the game without XBox One controller attached.

 

[CedricSysAdmin]

I am having so much trouble but I have an i7 6700K. Using ge force optimal settings I only hit 60 fps. 1080p @ 60hz. That did solve your issue?