This article explains it a bit.
"a point-based magic system, which is described herein. It actually made it a bit tougher to be a magic user, as spells typically took a full round to cast and then went off the next round, with rules for being damaged while casting and losing the spell in progress, based on the ratio of damage taken to your
current hit points (meaning, you needed to recalculate each time you were hit, as the threshold would change), and the number of spell points you got back each day (after 12 hours of sleep — none of this wimpy eight hours crap!) was based on your intelligence and how much you’d used… so you if you shot your wad completely, you wouldn’t be fully recharged by the next day. A very ahead of its time system, frankly. "
I started attending Princecon back with Princecon 17 when the Mahler spell system was still very much in use. Great convention, very different than any others. This year is Princecon 45 - I have my ticket but it was postponed from it's usual Princeton spring break weekend due to coronavirus and it's not in October. Though we switched to 5e a few years ago, and before that a modified version of 3.5, so Mahler system isnt' around any more. The PDFs of the Con books should be available to the public somewhere, maybe our web page. ("Our" is presumptuous - I did help run and DM for several years, but I've been in a haitus for a few. But still I'm protective of it, so "our".)
As a convention, it's more like a mini campaign. It's a bunch fo DMs with 4-6 linked sessions, all that are part of the metaplot that is going on in the setting of the year. DMs cross fertilize with clues and items needed/useful for other DMs, and sometimes even there are crossovers between runs of different DMs. You create a 5th level PC when you show up and keep them all weekend, gaining XP and items, ending around 9-11th if you game the whole time.
There are no slots, games run as long as they run and it is not uncommon for players to come back early without accomplishing all the imagined goals or go past what the DM envisioned as the end and accomplish more. Actually, player success is not counted on, and DMs are changing later scenarios on the fly based on the results of earlier scenarios and changes that affect the meta-plot. I've many time had a runner from Hireling Hall (the front desk and where you form up parties) come to the room I'm running to let me know about some world-spanning change that the players can/will notice right now, mid-run.
When you get back to Hireling Hall, you can sleep, eat, or grab a party, a waiting DM, and go back out. There were years back in university where I would sleep just cat-naps between runs and go for the 46 hours of runs (and another 2 hours of wrap up) on just those.
Magic items are given out on item cards we sign with our "magic pens", and can be freely traded or given between players on a run or at Hireling Hall. It's a regular thing that happens, cards getting to those who can use them the best.
At the end, the DMs have a (frantic) conversation about the results of the various runs on the over-plot, and then come out and give a wrap up to the players in what they succeeeded in. It's often bittersweet, with players generally succeeding but at cost, as some things go great and others the plaeyrs were unable to accomplish. They they finsih it up with a quick(ish) overview from each DM of their runs, and some amusing stories like "With Friends Like These..." about characters that inadertantly (usually) screwed over others. And awards.
Not like any other convention, no dealer rooms, slots, or other games. It's run by their undergraduate Simulations Games Union, those there was some lean years the SGU had just a handful of undergrads and the con was done mostly by alumni and others, but that's reversed and the SGU is happy and active.
If you're in NJ, US this October or any upcoming March and want to drop $20 on a full weekend of gaming, give it a try. It's my favorite convention by far.
EDIT: I just got around to reading the article. Wow, some of the rough edges were gone by the time of Pcon 17. As was Howard Mahler. But not Bob West. Referred to with his full "Robert West" in the articel, Bob West was the only person to attend every Princecon from the first until Princecon 42. He passed in October of 2017, but he was an absolute joy to be a player with or to run alongside. Known for very long runs full of lot and lots of RP. I still tell Bob West RP stories that happened decades ago. Raise your glass.