If you're still interested, here's a rundown of 1ed psionic combat.
A psionic character has a number of psionic strength points (from 5 to 172) for attack and the same number for defense. Total psionic strength is attack strength + defense strength.
Creatures in mental combat choose an attack mode and a defense mode from those they can use. The DM looks at a chart cross-referencing the attacker's current total psionic strength (in increments of 25) with the attack mode used and the defender's defense mode used. In most cases, the defender loses defense strength. Psychic crush is different in that it lists a chance to instantly kill the defender. Then the sides would switch with the attacker being the defender and vice versa. Once that was done, the damage and the costs of the attack and defense modes are subtracted from the respective strengths.
When a defender does not have enough defense strength to use a defense mode, the DM would use a second table comparing the attacker's current attack strength and attack mode to the defender's original total psionic strength. The defender starts losing attack strength points or has various other effects happen to him, such as losing attack or defense modes permanently or becoming a puppet. Psychic crush has a much greater chance of killing the defender at this point.
