int8 mode is different between 1080ti with 2080ti

AI & Data Science Deep Learning (Training & Inference) TensorRT
1

1080ti env： 2080ti env：
cuda9.0 cuda10.0
cudnn7.5 cudnn7.5
python3.7 python3.7
TensorRT5.1.2 TensorRT5.1.2
ubuntu16.04 ubuntu16.04

set max batch size 32，under 1080ti，yolov3 int8 trt model is 60M，but get 126M int8 model under 2080ti. besides, i notice that there is just a little difference between int8 and fp16 mode under 2080ti, trt model size are both near 120M. Is this normal?