I have to clarify the thread title a bit.

"i5 series quad processor"

i5 processors have 2 cores, except for the 2 lowest end models they all support hyperthreading thus able to run 4 threads, but they are NOT quad core prosessors as i7 are.

Hyperthreading seen by operating system as 4 (i5)  or 8 (i7) (virtual)cores is not equal to having 4 or 8 real physical cores.