There are 2 possibilities Read Speed: ----------- Different CDs and players have different read / write speeds. Quite often the player will adjust it's speed depending on the CD. However this is usually only during *write* so this doesn't seem to be the reason here, unless, the disk has issues being read at the highest player speed, in which case it may slow down to get a more reliably read the data. As these are all playstation CDs for playstations to read, this is unlikely. Location of Data: ----------------- CDs are read at a constant linear rate. This means that at the read head the CD must travel over it at a constant speed. Data on a CD has the same size per bit on the inside and outside, meaning that there is more data per revolution on the outside of the disc. Therefore, to provide a constant speed of data input over the reading head, the disc spins slower when reading the outside. Because of this, if the game needs to constantly read data that is near the outside of the disk, it will spin slower It's most likely that this is the reason why some seemed to spin slower than others [Source 1][1] [Source 2][2] [1]: https://en.wikipedia.org/wiki/CD-ROM [2]: https://arstechnica.com/civis/viewtopic.php?f=11&t=512455