Just realized that I think its beacause I've had these CD's in storage for 12 years, that they can burn at 4x. Glad I hung on to them! I guess. Although I don't have problems generally with my ps1 reading burned discs.
Nero Discspeed is a good utility for information, I have made a "portable" version, not sure if it will work, but I will attach it at the bottom,
maybe you can test it for me, if not it can be downloaded
(installer version yuck)
https://www.videohelp.com/software/Nero-CD-DVD-Speed
Also attached is a picture of the CD's from storage LOL
Untitled.jpg
Pretty sure that they do burn at 4x because it takes FOREVER haha