GD-ROM

From Redump Wiki

GD-ROM discs are a proprietary type of disc developed by Sega and Yamaha that can store up to one gigabyte of data. This format was mostly known to be used on the Dreamcast. The format is unique because there's a single density layer and a high density layer, the former can be read on any drive that supports CDs.

Denon, Maxell, Sanyo-Verbatim, and WEA manufactured the discs sold in the US, and Technicolor manufactured a couple games. At the console launch, some discs manufactured by Sanyo-Verbatim had been faulty. Memory-Tech and Nippon Columbia manufactured the discs sold in Japan. EMI manufactured the discs sold in Europe.