Pinout diagram
Summary specifications
Full pin reference
| Pin | Name | Group | Direction | Levels | Description |
|---|---|---|---|---|---|
| 1 | NC | No Connect | Not connected | No connect | No connect. On the 4116 this pin is VBB (-5 V); on the 41256 it becomes A8. |
| 2 | DIN | Data Bus | Input | TTL, 0 V / 5 V | Data input. Separate from DOUT (pin 14) because it is a x1 device. Eight chips make a byte. |
| 3 | /WE | Control | Input | TTL, active low | Active low. Write Enable. Low writes DIN into the selected address. |
| 4 | /RAS | Control | Input | TTL, active low | Active low. Row Address Strobe. Latches the row address from A0-A7. |
| 5 | A0 | Address Bus | Input | TTL, 0 V / 5 V | Address bit 0. The address pins are scrambled: A0 (5), A2 (6), A1 (7) — A2 and A1 are swapped — then A7 (9), A5 (10), A4 (11), A3 (12), A6 (13). Eight lines multiplexed by /RAS and /CAS give 256 x 256 = 65,536 bits. |
| 6 | A2 | Address Bus | Input | TTL, 0 V / 5 V | Address bit 2. Note A2 is on pin 6 and A1 on pin 7 — swapped relative to numerical order. |
| 7 | A1 | Address Bus | Input | TTL, 0 V / 5 V | Address bit 1. |
| 8 | VCC | Power | Power | +5 V | Positive supply, +5 V. This is pin 8, NOT pin 16 — the reverse of almost every other 16-pin DIP. On the 4116 this pin is +12 V VDD. Apply 5 V to pin 16 and you destroy the chip. |
| 9 | A7 | Address Bus | Input | TTL, 0 V / 5 V | Address bit 7. On the 4116 this pin is VCC (+5 V) — another reason the two are not interchangeable. |
| 10 | A5 | Address Bus | Input | TTL, 0 V / 5 V | Address bit 5. |
| 11 | A4 | Address Bus | Input | TTL, 0 V / 5 V | Address bit 4. |
| 12 | A3 | Address Bus | Input | TTL, 0 V / 5 V | Address bit 3. |
| 13 | A6 | Address Bus | Input | TTL, 0 V / 5 V | Address bit 6. |
| 14 | DOUT | Data Bus | Output | TTL, 0 V / 5 V | Data output. Separate from DIN (pin 2) because it is a x1 device. |
| 15 | /CAS | Control | Input | TTL, active low | Active low. Column Address Strobe. Latches the column address from A0-A7. |
| 16 | GND | Ground | Power | 0 V | Ground. This is pin 16, NOT pin 8 — the reverse of almost every other 16-pin DIP. Applying +5 V here destroys the chip. |
Common uses and repair diagnostics
The 4164 is a 65,536-word x 1-bit dynamic RAM — the single +5 V part that replaced the 4116's three rails and quadrupled the capacity. The headline trap is the supply: VCC is pin 8 and GND is pin 16. On a 16-pin DIP almost everything else puts VCC at pin 16 and ground at pin 8 — this part is the exact reverse. Apply 5 V to pin 16 and you destroy the chip. See the 4116 page for the destructive-swap comparison: a 4164 in a 4116 socket gets +12 V on its 5 V supply pin and will not survive.
The 4164 is a 65,536-word x 1-bit dynamic RAM. Used in the Commodore 64 (eight of them), the ZX Spectrum 48K issue 3 and later, the Amstrad CPC, the BBC Micro Model B upgrades, the MSX, the Apple IIe and almost every mid-80s machine. Single +5 V rail, which is the whole point: it replaced the 4116's three rails and quadrupled the capacity.
The headline trap is the supply: VCC is pin 8 and GND is pin 16. On a 16-pin DIP almost everything else puts VCC at pin 16 and ground at pin 8 — this part is the exact reverse. Apply 5 V to pin 16 and you destroy the chip. See the 4116 page for the destructive-swap comparison: a 4164 in a 4116 socket gets +12 V on its 5 V supply pin and a 5 V rail driven into an address input. It will not survive. Going the other way, a 4116 in a 4164 socket gets 5 V where it needs 12 V and an address line where it needs its 5 V rail, so it simply will not work. Adapter boards exist precisely because of this.
Address pins are scrambled, and note that A2 and A1 are swapped on pins 6 and 7: A0 (5), A2 (6), A1 (7), A7 (9), A5 (10), A4 (11), A3 (12), A6 (13). Eight lines multiplexed by /RAS and /CAS give 256 x 256 = 65,536 bits. Separate DIN (2) and DOUT (14); a x1 device, so eight chips make a byte. A single failed 4164 therefore corrupts ONE BIT of every byte in the bank — which is why a failing C64 or Spectrum often still boots but shows garbled characters or a wrong BASIC byte count rather than nothing at all. That symptom is the useful diagnostic.
The 41256 (256K x 1) uses the same pinout with pin 1 becoming A8, so it is close to a drop-in where the board can drive the extra line. The 41464 is the 64K x 4 version in an 18-pin package and is NOT pin compatible.
- On a C64, a dead 4164 usually gives a garbled or flickering boot screen rather than a blank one, and the corrupted character pattern repeats.
- Confirm 5 V on pin 8 (not 16). Applying 5 V to pin 16 destroys the chip.
- Check /RAS (pin 4) and /CAS (pin 15) are being strobed. No strobes means no refresh and no data.
- A chip running noticeably hotter than its neighbours is the usual culprit — feel along the row.
- A single failed 4164 corrupts one bit of every byte — garbled characters or a wrong BASIC byte count, not a dead machine.