2364 Mask ROM 8K×8 pinout

DIP-24. BASIC and KERNAL ROMs (C64); BASIC and KERNAL (VIC-20, PET); character ROM (C128)

8K x 8 mask ROM in 24 pins, with one mask-programmed chip select on pin 20 and A12 on pin 21. Rarely fails. A 2764 EPROM needs a 24-to-28-pin adapter. Garbage on boot or a dead KERNAL points here. IBM PC 5150: the spare ROM socket U28 beside U29-U33 is empty as shipped; Technical Reference 6025008 draws each ROS as 8K x 8 with A11 on pin 18, /CS on 20 and A12 on 21. Atari 800XL: the FSM schematic draws the BASIC ROM U4 with the same A11 (18), /CS (20) and A12 (21) wiring.

Open the interactive 2364 pinout

Pins

Pin	Name	Type	Signal
1	A7	addr	Address bit 7.
2	A6	addr	Address bit 6.
3	A5	addr	Address bit 5.
4	A4	addr	Address bit 4.
5	A3	addr	Address bit 3.
6	A2	addr	Address bit 2.
7	A1	addr	Address bit 1.
8	A0	addr	Address bit 0.
9	D0	data	Data out bit 0.
10	D1	data	Data out bit 1.
11	D2	data	Data out bit 2.
12	GND	ground	0 V.
13	D3	data	Data out bit 3.
14	D4	data	Data out bit 4.
15	D5	data	Data out bit 5.
16	D6	data	Data out bit 6.
17	D7	data	Data out bit 7.
18	A11	addr	Address bit 11.
19	A10	addr	Address bit 10.
20	CS	ctrl	Chip select. Polarity is mask-programmed (CS or /CS).
21	A12	addr	Address bit 12.
22	A9	addr	Address bit 9.
23	A8	addr	Address bit 8.
24	VCC	power	+5 V supply.

Fitted in

Commodore 64 U3 (BASIC 901226), U4 (KERNAL 901227)
VIC-20 UE11 (BASIC 901486-01), UE12 (KERNAL 901486-06/-07)
PET / CBM
Commodore 1541 disk drive UB3 ($C000, 325302-01) and UB4 ($E000, 901229) on short boards; UAB4 ($C000) and UAB5 ($E000) on the long board
Commodore 128 U18 (character ROM 390059-01, 2364-318; some national versions fit a 2764 EPROM)
Atari 800XL U4, BASIC ROM 8K x 8 (C024947A-01 on the photographed board)
TRS-80 Model III U104 (ROM A, MCM68A364)
TRS-80 Model 4 U68 (MCM68A364)
IBM PC 5150 U29-U32 cassette BASIC (5700019, 5700027, 5700035, 5700043) and U33 BIOS (5700051 on the photographed board)

2364 Mask ROM 8K×8 pinout

Pins

Fitted in

Sources