SEGA SC-3000 Memory system

SEGA SC-3000/SG-1000 have a z80 microprocessor that is able to handle 64Kbytes of memory.

This range is usually mapped as ROM and RAM, where the cpu can access the software stored in ROM, and use RAM as a work space.

They have a main RAM onboard memory of 2Kbytes, and used generally by games. A ROM game can occupy 8, 16 and 32 Kbytes, but there are some that reach up to 40Kbytes.

There are other ROM cartridges such as BASIC programming languages and MUSIC editor that have their onboard RAM, that will be mapped as extra RAM and will disable the main 2k on mother board. 

So a typical address ranges can be:

Configuration

ROM MAP

RAM MAP
GAMES

0x0000 ~ 0x1fff
0x0000 ~ 0x3fff
0x0000 ~ 0x7fff
0x0000 ~ 0x9fff

0xC000 ~ 0xC800
APPLICATION ( Basic, Music...) 0x0000 ~ 0x7fff 0x8000 ~ 0xFFFF *


(*) RAM Memory will be different for different version of BASIC, and can be used only with SC-3000 or SG-1000 with external keyboard SK1100:
    BASIC LEVEL II A: no extra RAM
    BASIC LEVEL II B: 8 Kb RAM
    BASIC LEVEL III A: 16 Kb RAM
    BASIC LEVELIII B: 32 Kb RAM

We will be able to use 64Kbytes of the memory we need by using the SRAM of C3.