in cases of disk read bottleneck i would recommend a pcie sata III add on pc card that in conjunction with high end graphics card would really slice nonce reading times like butter. USB3 drives have in my case read faster with an addon card for that too simply that it isn't integrated into the motherboard. Like Haitch said, your read time is on par with proper read speeds. My cpu is simular to yours @eneloop i recommend not to use its gpu cores. Components don't have to be brand new. I've had my nvidia GT730 low profile passive cooled GPU for several years and been mining with it for over 6 months it has kept the pace for mining as i use xplotter for plotting. There's the power profile management in control panel with CPU adjustments that the minimum can be set to 100% which is healthier on desktops that they have no battery. That could set your gpu cores to be less latent. BUT being integrated into cpu it might not do anything but cpu will maintain top frequency even when idle. jminer can be manually configured to device id of your gpu cores they can be listed with the gpu ploting tools command switches to determine correct gpu address so as not to use cpu.