P4 chipset memory map

Memory location Purpose
0x0000-0x00ff Battery backed static ram
0x0100-0x01ff Non-battery backed static ram, cleared when the key is off
0x0200-0x03ff On chip SRAM in enhanced P4 MPUs
0x0400-0x04ff GM debugging HUD ram variables (if present)
0x3dc0-0x3dff Extra timer chip
0x3f80-0x3fbf Extra timer chip
0x3fc0-0x3fff P4 timer chip
0x4000-0x400f memory mapped I/O registers
0x5000-0x5fff GM debugging HUD hardware
0x5800-0x58ff GM debugging HUD code
0x6000-0x6fff GM debugging HUD code
0xc000-0xffff EPROM (27128, 16K EPROM, code and data)
0x8000-0xffff EPROM (27256, 32K EPROM, code and data)
0xfff0-0xfffe interrupt vectors

I/O registers

Interrupt vectors