The (i)sc - element in romance verb cojugation

In the romance verb, the stem of verbs are in some forms extended by
an element -i(sc)- or some modifiction of this. It is used in
different ways, and in different degree in the different languages.
However it is best attested in Italien in the 3. conjugation where it
is very much used and very productive(= Latin 4. conjugation).

For eksample: capisco, capisci, capisce, capiscono (I, you, he, they
understand)

It is also found in some verbs of Italian 2. conjugation (If it
really is the same element?) conosco, conosci, conosce. Etc. (I, you,
he know(s))

Latin had a group of verbs in the 3. cojugation called Inchoative
verbs with a -sc - element. The Italian verb Conoscere, I assume
belongs to that group.

But what is the origin of the element -isc in the Italian 3.
cojugation and elswere in the romance languages. Is it simply the
inchoative element from Latin that has analogically been transformed
to other places? Does anyone know?

This element, as far as I know has its origine back to PIE, where it
was used to form Iterative verbs, I think. Does anyone know somewhat
more of the prehistory of this element.

In either case, If the -isc-element in romance, indeed originates
from the Latin inchoative element, this is a funny example of a very
old element that has got an intresting renessance in modern
languages.