JEIDA V3 memory cards used in AES and some MVS systems to store game saves and/or high scores. The original SNK card could only hold 2KiB of data. The Neogeo can use up to 8MiB (24 address lines but A23 never used) ?

The official SNK memory card was a battery-based 2KiB card using a LH5116 CMOS SRAM chip and voltage switching circuitry. Data retention voltage: 2V.

The SP-S2 BIOS can only handle 8bit memory cards up to 16KiB ? (bank checking while format up to $8000/2). Seems the file checking can only go up to 256 so 16 files * 16 games * 64 bytes = 16KiB too.

Replaced by a 8KiB fixed battery-backed RAM chip in the CD systems.

See the CARD BIOS call description for memory card operations.

Data format

BIOS can handle 8 different card size (2K, 4K, 6K, 8K, 10K, 14K and 16K) and different card type (8 bits wide, 16 bits wide, 16 bits doubled wide and SNK ROM card).

All the data here are for all the card, it's just a matter on how to read the data between different type of card.

The internal card data are splitted into 5 regions.

Header

Always $80 bytes.

Address	Name	Size	Description
$0~$9		10 bytes	Zero or "SNK ROM " (Development unit I think) For 16bits doubled card, $6 is set to $0001
$A	CARD_SIZE	word	Size of the memcard
$C		byte	0
$D	CARD_FAT_1_CHKSUM	byte	Checksum of the FAT 1
$E	CARD_FAT_2_CHKSUM	byte	Checksum of the FAT 2
$F	CARD_USERNAME_AVAILABLE	byte	0 : Username available, !0 : Username unavailable
$10	CARD_USERNAME	16 bytes	Card holder username
$20	CARD_MAGIC	16 bytes	$4e $XX $45 $XX $4f $XX $2d $XX $47 $XX $45 $XX $4f $XX 80 $XX "NEO-GEO" + $80
$30	CARD_REGION	byte	Region of slot that formated the card, 0 = Japan, 1 = USA, 2 = Europe

FAT 1

List of used blocks. Size depends on card size, it can hold 64, 128 192 or 256 entries. $02 is a BIOS reserved block $01 is a game used block $00 is a free block

FAT 2

FAT 2 is simply a mirror of FAT 1.

Game Data

Normally 64 bytes but maybe some games use more that one block ?

The first 20 bytes are the data title (generally the game name + the stage name).

Card pinout

Pin	Goes to	Signal name	PC Card name
1	GND
2	9 G0	MCD3	D3
3	11 G0	MCD4	D4
4	12 G0	MCD5	D5
5	13 G0	MCD6	D6
6	14 G0	MCD7	D7
7	42, 27 C1	CRDC	/CE1
8	23 E0	Y10	A10
9	30 C1	CRDO	/OE
10	24 E0	Y11	A11
11	22 E0	Y9	A9
12	14 E0	Y8	A8
13	28 E0	Y13	A13
14	29 E0	Y14	A14
15	6 HC32	(31 C1 (CRDW) OR REG_CRDUNLOCK1 OR /REG_CRDUNLOCK2)	/WE
16	NC		READY
17	VCC
18	VCC
19	39 E0	Y16	A16
20	30 E0	Y15	A15
21	27 E0	Y12	A12
22	13 E0	Y7	A7
23	12 E0	Y6	A6
24	11 E0	Y5	A5
25	9 E0	Y4	A4
26	8 E0	Y3	A3
27	7 E0	Y2	A2
28	6 E0	Y1	A1
29	5 E0	Y0	A0
30	6 G0	MCD0	D0
31	7 G0	MCD1	D1
32	8 G0	MCD2	D2
33	88 C1	IN26 (REG_STATUS_B bit 6)	WP (Write Protect)
34	GND

Pin	Goes to	Signal name	PC Card name
35	GND
36	73 C1	IN24 (REG_STATUS_B bit 4)	/CD1 (Card Detect 1)
37	30 G0	MCD11	D11
38	43 G0	MCD12	D12
39	44 G0	MCD13	D13
40	45 G0	MCD14	D14
41	46 G0	MCD15	D15
42	7		/CE2
43	NC		/VS1
44	NC		/IORD
45	NC		/IOWR
46	40 E0	Y17	A17
47	41 E0	Y18	A18
48	43 E0	Y19	A19
49	44 E0	Y20	A20
50	45 E0	Y21	A21
51	VCC
52	VCC
53	46 E0	Y22	A22
54	47 E0	Y23	A23
55	NC		A24
56	NC		A25
57	NC		/VS2
58	NC		RESET
59	NC		/WAIT
60	NC		Reserved
61	8 HC32	(REG_CRDREGSEL OR CRDO)	/REG
62	NC		BVD2
63	NC		BVD1
64	27 G0	MCD8	D8
65	28 G0	MCD9	D9
66	29 G0	MCD10	D10
67	87 C1	IN25 (REG_STATUS_B bit 5)	/CD2 (Card Detect 2)
68	GND

Memory card

Contents