I'd have to check. But it used the same system of spell levels, class limited lists, maximum level spell attainable... and magic and psi resistance were defauled to (RAW) 100% cross effective; D&D OE and AD&D they were 0% cross effective.I thought I remembered 3e era psionics still using power points. Am I completely confused here?
It's worth noting that Rolemaster's approach to magic is grounded in D&D OE...
Channeling is drawing power from extraplanar beings
Essence is drawing power from one's immediate surroundings
Mentalism is drawing power solely from oneself.
If one has the Spacemaster box...
Psionics is very close to mentalism, but mechanically slightly different. Each has slightly different armor restrictions.