24S10 / 82S129 bipolar PROM 256 x 4 pinout
DIP-16. Memory address decoder: a 256 x 4 lookup table that turns high address bits into chip selects.
A 256 x 4 bipolar PROM used as a lookup table: eight address bits in, four select lines out. IBM programs it, so a blank 24S10 or 82S129 does nothing until it is burned with a dump of the original. A bad one gives missing or overlapping memory: wrong RAM size, no ROM, or a dead board. It runs warm.
Open the interactive 24S10 pinoutPins
| Pin | Name | Type | Signal |
|---|---|---|---|
| 1 | A6 | addr | Address input 6. |
| 2 | A5 | addr | Address input 5. |
| 3 | A4 | addr | Address input 4. |
| 4 | A3 | addr | Address input 3. |
| 5 | A0 | addr | Address input 0. |
| 6 | A1 | addr | Address input 1. |
| 7 | A2 | addr | Address input 2. |
| 8 | GND | ground | Ground. |
| 9 | Q3 | ctrl | Output 3. |
| 10 | Q2 | ctrl | Output 2. |
| 11 | Q1 | ctrl | Output 1. |
| 12 | Q0 | ctrl | Output 0. |
| 13 | /S1 | ctrl | Output enable 1, active LOW (grounded on both boards). |
| 14 | /S2 | ctrl | Output enable 2, active LOW (grounded on both boards). |
| 15 | A7 | addr | Address input 7. |
| 16 | VCC | power | +5 V. |
Fitted in
- IBM XT 5160 U44, RAM bank decode (XT Technical Reference 1502237, sheet 3 of 10, draws a 24S10); N82S129AN marked 6359123 on the photographed board
- IBM Portable 5155 U44 (same 64-256KB board as the XT); the marking is not legible on the photographed board
- IBM PCjr 4860 ZM56, memory decode: -VIDEO RAM CS, -ROM SEL and -MEM ON CARD (PCjr Technical Reference, sheet 5 of 17); TBP24S10N on the photographed board