Memory Map

The following article shows a short overview of the C64 memory map (pages and memory addresses) as seen by its CPU. The address space may look different from the view of other chips such as the VIC.

This overview shows the status after power on of the C64 in the standard memory configuration ($37/55 in memory address $01, no cartridge).

Detailed descriptions of every memory area can be found in the associated articles.

The memory management is implemented mostly by the C64 PLA.

Overview

Commodore 64 Memory Map Overview

The diagram on the right displays the addressable locations, and therefore the likely layout, of all memory within the C64. The following notes are meant to be cursory and provide direction to more detailed accounts.

Configurations

The default configuration is for KERNAL ROM, I/O, BASIC ROM and the remaining RAM banks to be visible to the CPU. All configurations depend upon the state of latch bits set in the Programmable Logic Unit (PLA). The 7 distinct RAM banks are the smallest zones which can be bank switched.

ROM vs RAM

If ROM is visible to the CPU during a write procedure, the ROM will be read but, any data is written to the the underlying RAM. This principle is particularly significant to understanding how the I/O registers are addressed.

Cartridge ROM

If cartridge ROM is present it can be located in up to three addressable locations. However, only two 8 kByte banks can be seen by the CPU at any time.

BASIC RAM

The BASIC program storage space crosses the boundaries of RAM zones, sitting between $0800-$9FFF (38911 BASIC bytes)

Memory Details

The exact content and purpose of each memory bank can be found in the RAM Table, ROM Table and I/O Table below.

RAM Table

Hex Address	Dec Address	Page	Contents
$0000-$00FF	0-255	Page 0	Zeropage addressing
$0100-$01FF	256-511	Page 1	Enhanced Zeropage contains the stack
$0200-$02FF	512-767	Page 2	Operating System and BASIC pointers
$0300-$03FF	768-1023	Page 3	Operating System and BASIC pointers
$0400-$07FF	1024-2047	Page 4-7	Screen Memory
$0800-$9FFF	2048-40959	Page 8-159	Free BASIC program storage area (38911 bytes)
$A000-$BFFF	40960-49151	Page 160-191	Free machine language program storage area (when switched-out with ROM)
$C000-$CFFF	49152-53247	Page 192-207	Free machine language program storage area
$D000-$D3FF	53248-54271	Page 208-211
$D400-$D7FF	54272-54527	Page 212-215
$D800-$DBFF	55296-56319	Page 216-219
$DC00-$DCFF	56320-56575	Page 220
$DD00-$DDFF	56576-56831	Page 221
$DE00-$DFFF	56832-57343	Page 222-223	Reserved for interface extensions
$E000-$FFFF	57344-65535	Page 224-255	Free machine language program storage area (when switched-out with ROM)

ROM Table

Cartridge ROM only becomes resident if attached to the expansion port on power-up. It is included for completeness as a record of the addresses it occupies as a ROM bank.

Hex Address	Dec Address	Page	Contents
$8000-$9FFF	32768-40959	Page 128-159	Cartridge ROM (low)
$A000-$BFFF	40960-49151	Page 160-191	BASIC interpretor ROM or cartridge ROM (high)
$D000-$DFFF	53248-57343	Page 208-223	Character generator ROM
$E000-$FFFF	57344-65535	Page 224-255	KERNAL ROM or cartridge ROM (high)

I/O Table

Hex Address	Dec Address	Page	Contents
$0000-$0001	0-1	-	CPU I/O port - see Zeropage
$D000-$D3FF	53248-54271	Page 208-211	VIC-II registers
$D400-$D7FF	54272-55295	Page 212-215	SID registers
$D800-$DBFF	55296-56319	Page 216-219	Color Memory
$DC00-$DCFF	56320-56575	Page 220	CIA 1
$DD00-$DDFF	56576-56831	Page 221	CIA 2
$DE00-$DEFF	56832-57087	Page 222	I/O 1
$DF00-$DFFF	57088-57343	Page 223	I/O 2

Links

• Mapping the Commodore 64 on Bo Zimmer's Commodore web pages
• All About Your 64 texts including complete ROM disassembly and memory map