🏠 Atari Jaguar Developer Reference ▸ Architecture & Memory ▸ Cartridges, EEPROM Saves & ROM Building

Cartridges, EEPROM Saves & ROM Building

The Jaguar cartridge port, saving data to the on-cartridge serial EEPROM, and the EPROM/EEPROM parts for building your own test cartridges. This is hardware-level information and is independent of any particular toolchain.

Source: Technical Reference Manual (V10), pp. 32–34 (Cartridges and NVRAM, Burning Your Own Cartridge EPROMs, EPROMs/EEPROMs for Making Cartridges). © Atari Corp. 1995.

The cartridge port

Up to 6 MB of cartridge space, mapped at $800000 (see Memory Map).
Cartridges may be 8, 16, or 32 bits wide. Note: the Stubulator ROM in development machines currently supports 32-bit-wide cartridges only.
Program code always starts at $802000 in both encrypted and non-encrypted cartridges.
In a non-encrypted test cartridge, $800000–$801FFF must be all $FF (in an encrypted cartridge this region holds the security code — see the reserved ROM area).

EEPROM saves (NVRAM)

Cartridges may include a small serial EEPROM for high scores, options, and other persistent data.

Read/write only through the Atari-supplied routines (see the NVRAM sample program / SOURCE\EEPROM). That is the only way to guarantee reliable operation — do not bit-bang the EEPROM yourself.

Two cautions:

JOYSTICK bit 0 is overloaded. When read, bit 0 of the JOYSTICK register ($F14000) returns the EEPROM data-output bit, not the J0 joystick input. J0 has always been used as an output, so this rarely matters — but treat that read bit as random, not as the J0 level. See Controllers and Memory Map.
Keep clear of the EEPROM’s address range. The EEPROM uses addresses in the GPIO0/GPIO1 range $F14800–$F15FFF. Any inadvertent access (read or write) to that range makes subsequent EEPROM reads/writes fail — so don’t touch it. See Serial I/O → GPIO decodes.

Building your own test cartridges

32-bit EPROM byte ordering (4-chip Atari blanks)

When building 32-bit test cartridges on Atari’s 4-chip EPROM cartridge blanks, data is split across the chips like this:

Chip	Byte addresses	Bits in the 32-bit long
U1	`$800003`, `$800007`, `$80000B`, …	d0–d7
U2	`$800002`, `$800006`, `$80000A`, …	d8–d15
U3	`$800001`, `$800005`, `$800009`, …	d16–d23
U4	`$800000`, `$800004`, `$800008`, …	d24–d31

EPROM burner

Any EPROM burner capable of handling 4-megabit chips should work. Atari had good results with the Pilot EPROM burners (manufactured by Advin).

EPROM types (game code)

EPROM types Atari’s test department used successfully (slower access speeds than shown are not recommended; similar chips from other makers are untested):

Cartridge	Configuration	Manufacturer	Chip code
1 MB (4×4 + 128-byte EEPROM)	(4) 512 Kbit × 8 — 4 Mbit	Macronix	`MX27C4000DC-12`
		Toshiba	`TC574000AD-120` / `TC574000AD-150`
		AMD	`AM27C040-150DC`
		(generic)	`27C400`
2 MB (16×2 + 128-byte EEPROM)	(2) 512 Kbit × 16 — 8 Mbit	—	`27C800`
4 MB (16×2 + 128-byte EEPROM)	(2) 1024 Kbit × 16 — 16 Mbit	—	`27C160`
6 MB (16×2 + 128-byte EEPROM)¹	(2) 2048 Kbit × 16 — 32 Mbit	—	`27C322`

¹ 6 MB requires modified Atari PCBs or new non-Atari PCBs.

EEPROM types (game saves)

Manufacturer code	Size	Notes
`93c46b`	128 byte	Atari PCBs & duplicates
`93c46c`	128 byte	alternate PCB designs
`93lc46c`	128 byte	alternate PCB designs
`93c86b`	2 KB	Atari PCBs & duplicates
`93c86c`	2 KB	alternate PCB designs
`93lc86c`	2 KB	alternate PCB designs