CD-ROM vs Super CD-ROM?

[akirashinigami]

What exactly was the difference between them?

[SignOfZeta]

CDROM games run with the system card that came with the CD attachment. Super CDROMs required a different system card that was released separately later. This card was basically a new DOS and some RAM.

When the Duo was released it included all the Super CD capabilities.

[Bonknuts]

 The original CD unit didn't have adequate ram which restricted games and increased load times. The SCD increased the memory by 4 times. I should point out that most CD games are guilty of wasting memory (ram) - because they didn't even bother compress graphics which would have made room for more animation and tiles/sprites :/  Some of the later regular CD games were very efficient though like Valis 3, (and especially ) Valis 4, the first Spriggan. SCD games like GOT and LOT used compression through out the game - I wish more SCD games did this.

[Necromancer]

In addition to what has already been said, here's the numbers for you (including one you didn't ask for, 'cause I'm feeling generous).

CD-ROM: .25 megabits o' memory
Super CD-ROM: 2 megabits o' memory
Arcade CD-ROM: 18 megabits o' memory