The NAOMI and Dreamcast share the same system-architecture. Both systems use the same Hitachi SH-4 CPU, PowerVR Series 2 GPU (PVR2DC), and Yamaha AICA based sound system. NAOMI packs twice as much system and graphics memory, and 4X as much sound memory. And although the NAOMI and Dreamcast operate at the same speed (clock frequency), multiple NAOMI boards can be 'stacked' together to achieve better graphics performance or a multi-monitor setup. The other key difference between NAOMI and Dreamcast lies in the game-media. The Dreamcast typically loads data from a GD-ROM during a game. NAOMI games either use only solid-state ROMs without a GD-ROM, or else load data from a GD-ROM only once at the start of a game to avoid wear and tear on the hardware. The NAOMI system is capable of storing 168 MB of data.