8087 numeric data processor pinout
DIP-40. Optional floating-point coprocessor in the empty socket beside the 8088.
Sits on the same local bus as the 8088 and watches its queue status (QS0, QS1) to pick out its own instructions. BUSY drives the 8088 /TEST pin; RQ/GT0 asks the 8088 for the bus. On the 5150 (socket U4) /RQ/GT0 goes to 8088 pin 30 (RQ/GT1) and INT goes to NMI through the coprocessor-installed switch logic, not to the 8259A. It runs hot. The shared bus pins sit on the same pin numbers as on the 8088.
Open the interactive 8087 pinoutPins
| Pin | Name | Type | Signal |
|---|---|---|---|
| 1 | GND | ground | Ground. |
| 2 | A14 | addr | Address bit 14 (AD14 with an 8086). With an 8088 the 8087 drives A15 to A8 for T1 to T4. Pins 2 to 8 are A14 to A8. |
| 3 | A13 | addr | Address bit 13. |
| 4 | A12 | addr | Address bit 12. |
| 5 | A11 | addr | Address bit 11. |
| 6 | A10 | addr | Address bit 10. |
| 7 | A9 | addr | Address bit 9. |
| 8 | A8 | addr | Address bit 8. |
| 9 | AD7 | data | Multiplexed address and data bit 7. Inputs while the CPU owns the bus. |
| 10 | AD6 | data | Multiplexed address and data bit 6. |
| 11 | AD5 | data | Multiplexed address and data bit 5. |
| 12 | AD4 | data | Multiplexed address and data bit 4. |
| 13 | AD3 | data | Multiplexed address and data bit 3. |
| 14 | AD2 | data | Multiplexed address and data bit 2. |
| 15 | AD1 | data | Multiplexed address and data bit 1. |
| 16 | AD0 | data | Multiplexed address and data bit 0. |
| 17 | NC | nc | Not connected. |
| 18 | NC | nc | Not connected. |
| 19 | CLK | clock | Clock, 33 percent duty, the same CLK as the CPU. |
| 20 | GND | ground | Ground. |
| 21 | RESET | ctrl | Reset, active HIGH for at least four clocks. |
| 22 | READY | ctrl | Ready, active HIGH, from the 8284A. |
| 23 | BUSY | ctrl | Busy, active HIGH while a numeric instruction runs, and after an unmasked exception. Goes to the CPU /TEST pin. |
| 24 | QS1 | ctrl | Queue status bit 1 from the CPU (pin 24). |
| 25 | QS0 | ctrl | Queue status bit 0 from the CPU (pin 25). |
| 26 | /S0 | ctrl | Status /S0. Driven when the 8087 owns the bus; monitored otherwise. |
| 27 | /S1 | ctrl | Status /S1. |
| 28 | /S2 | ctrl | Status /S2. |
| 29 | NC | nc | Not connected. |
| 30 | NC | nc | Not connected. |
| 31 | /RQ/GT0 | ctrl | Request/grant 0, to one of the CPU request/grant pins. |
| 32 | INT | ctrl | Interrupt, active HIGH, on an unmasked numeric exception. |
| 33 | /RQ/GT1 | ctrl | Request/grant 1, for another local bus master. Internal pull-up; may be left open. |
| 34 | /BHE/S7 | ctrl | Bus high enable and status S7. Not used with an 8088 (HIGH in maximum mode). |
| 35 | A19/S6 | addr | Address bit 19 and status S6. |
| 36 | A18/S5 | addr | Address bit 18 and status S5. |
| 37 | A17/S4 | addr | Address bit 17 and status S4. |
| 38 | A16/S3 | addr | Address bit 16 and status S3. |
| 39 | A15 | addr | Address bit 15 (AD15 with an 8086). |
| 40 | VCC | power | +5 V supply. |