Dull edge

Anything that is technologically obsolete and out of date; The opposite of cutting edge; the extreme opposite of bleeding edge.

I can't use my old dull edge computer because it has only a painfully slow Core 2 Duo processor.
My father still have a Pentium 3 computer processor on my attic, it's a dull edge processor from 1990's.
I wonder why they are still using some dull edge computer machine for running up our computer laboratorium.