a strange bottleneck

Islam Ghunym · February 2, 2019

I have mATX ASUS motherboard with I3-8100

1 stick of 8 gigs team group 2400 Mhz memory (single channel)

2 TB barracuda seagate HDD + 120 GB SATA III samsung SSD

Nvidia GTX 1060 3 GB

Now let me explain the bottleneck:

It appears only if I was using the intel UHD 630 IGP in some old games for better power saving.

I experienced it in metro last light game and that was only in the last chapter when the reds attack the station so the PC have to deal with many actions happening in the field, that is why I thought it may be a CPU bottleneck, but hold on I3-8100 is a prety decent CPU for gaming and it won't lag in old games!

the lag disapears on Nvidia GPU I so I thought it could be the IGP then lowered the textures from normal to lowest and the resolution from FHD to 800 × 600, but lags remained exactly the same however the game was good on FHD why only in the last chapter! when many events happens so I used some hardware monitoring tools to notice that: along with the lag the CPU usage and the IGP was droping to nearly none around 12% 3% 4% 8% for each core in the CPU individually and about 80-60-20-4% of the IGP usage, so it is not the IGP nor the CPU and I can't blame my good amount of memory of course since 8 gigs is more than enough

in another game (mount & blade warband) which is a prety light and old game.

during battles the bottleneck appears as a frame droping from around 50 to a complete lags exactly like metro last light in the last chapter while none of the cpu or the IGP was being used!

the lag appears when the 2 armies hit each others.

at the start of the battle with both teams are moving (cavalaries rushing, archers drawing, infantries running) performance fine, but when the 2 teams hit each others in the middle of the battlefield, lags start heavily and whatever I try to do to lower the lag by looking at some areas with no details like the sky or outside the battle range I never success so could it be ram timing matter or bad learning algorithms since the IGP and the CPU has to share the single chanel bandwidth but single channel DDR4 2400 is much more than good for this, so what could it be????