GTA 5 loss of frame rate

Jacob_G

Honorable
Mar 25, 2013
37
0
10,530
Most of my system:
GPU: Sapphire Radeon HD 7970 ghz edition (OC to 1160/1620)
CPU: Intel Core k7 3770K @3.50 GHz (4 cores & 8 thread, family 6, model A, Revision E1/L1)
RAM: 8 Gb DDR3, dual channel
HDD: LaCie d2 Quadra v3 USB Device (externally attached via usb 3.0)
PSU: very good 750 Watt (easily enough for everything)

My problem:
When I am running the game it often operates at 60fps, however during intense scenes of action (driving, fighting etc.), the fps will occasionally drop dramatically. It usually goes down to 50 which is annoying but not unbearable, however it occasionally drops to 40 or even 30. I have been attempting to track my system resources to identify the bottleneck, however I have been largely unsuccessful due to insufficient knowledge of what to measure and how. According to GPU-Z, my gpu usage never goes much beyond 80% so that doesn't seem to be the issue. I have tried various techniques to measure my HDD speed, memory and cpu however each attempt ends in confusion or data that says that nothing is ever maxed out while playing. Clearly I am doing something wrong and would like some help figuring this out. Thanks.