so after repairing that ps2 fat yesterday, i noticed that it wasn't playing back Ico properly. the disc would attempt to spin up for a half second, retry several times, then give up for good.

the disc was in perfect shape.

i noticed that it was a blue/purple bottomed disc, which made me curious. as it turns out, the blue discs are CD-ROMs. there are very few of them for the PS2, and then almost always cause read problems.

in the 00's teenagers figured out that if you put two pieces of masking tape on opposite sides of the spindle hole of a CD, the PS2 would read the game properly. i was perplexed by this, because i couldn't find any explanation of why the "tape trick" worked. was it shimming a gap between the disc and the tray?

as it turns out, a very young kid named Denzel explained it perfectly in his 16 year old 3gp cell phone video:
https://www.youtube.com/watch?v=iaaRs_H5Fjc

the problem is caused by a weak magnet used in the tray that hovers over the spindle. seen below, this white piece of plastic clamps down on top of the CD's "clamping area" (the perimeter of the donut hole). it is meant to both hold the disc level, *and* prevent the disc from slipping on the spindle.

since putting downforce weight/pressure on the spindle is a Bad Idea (motors don't love this), engineers embedded a magnet in the white plastic: when the plastic came close to the metal spindle, the magnetic forces sandwich CD between the spindle and white plastic. with enough magnetic grip, the CD wouldn't slip at all.

it works great for DVDs that spin at 4x.

unfortunately the PS2 engineers did not consider at least three things:
- playstation CD-ROMs are much heavier and more difficult to spin than DVDs, requiring more friction from the spindle.
- the CD-ROM in the ps2 spins at 24x. the motor goes into jet engine mode when it detects a CD. it needs *much* more sticky friction to keep that CD from slipping when the motor is sending your disc off into orbit.
- the cheapass fridge magnet inside of the plastic disc would lose their magnetism over time - due to various factors (EM fields, shock, heat). even a tiny percent change was enough to let a CD disc slip.

the solution? i stole a tiny strong button magnet from one of my fridge magnet toys. it very easily centered on the existing magnet, without needing glue.

this is information now buried in hundreds of shitty youtube videos and reddidiots *still* telling people to stick tape on their CDs.