P5 boot PROM 341-0027 (256 × 8, 6309 type) pinout
DIP-20. Controller boot code at $Cn00-$CnFF
The 256-byte boot program the Autostart ROM finds at $Cn00 ($C600 in slot 6): PR#6 runs it, it recalibrates the head against the stop and reads track 0, sector 0. 341-0027 is the 16-sector (DOS 3.3) part; 341-0009 is the 13-sector (DOS 3.2) one. Its +5 V (pin 20) is switched on only while /I/O SELECT is LOW, so 0 V there at rest is normal. Not a 74S287/82S129: those are 256 × 4 in 16 pins.
Open the interactive P5 pinoutPins
| Pin | Name | Type | Signal |
|---|---|---|---|
| 1 | A0 | addr | Address 0: AD0 (slot pin 2). |
| 2 | A1 | addr | Address 1: AD1 (slot pin 3). |
| 3 | A2 | addr | Address 2: AD2 (slot pin 4). |
| 4 | A3 | addr | Address 3: AD3 (slot pin 5). |
| 5 | A4 | addr | Address 4: AD4 (slot pin 6). |
| 6 | O1 (D0) | data | Data bit 0 to the slot data bus. |
| 7 | O2 (D1) | data | Data bit 1 to the slot data bus. |
| 8 | O3 (D2) | data | Data bit 2 to the slot data bus. |
| 9 | O4 (D3) | data | Data bit 3 to the slot data bus. |
| 10 | GND | ground | 0 V. |
| 11 | O5 (D4) | data | Data bit 4 to the slot data bus. |
| 12 | O6 (D5) | data | Data bit 5 to the slot data bus. |
| 13 | O7 (D6) | data | Data bit 6 to the slot data bus. |
| 14 | O8 (D7) | data | Data bit 7 to the slot data bus. |
| 15 | /E1 | ctrl | Output enable 1, active LOW. Tied to ground on the card. |
| 16 | /E2 | ctrl | Output enable 2, active LOW: /I/O SELECT from slot pin 1, so the PROM answers at $Cn00-$CnFF. |
| 17 | A5 | addr | Address 5: AD7 (slot pin 9; the card crosses A5 and A7). |
| 18 | A6 | addr | Address 6: AD6 (slot pin 8). |
| 19 | A7 | addr | Address 7: AD5 (slot pin 7; the card crosses A5 and A7). |
| 20 | VCC | power | +5 V, switched: Q1 (2N3906) and Q2 (MPSU51) power the PROM only while /I/O SELECT is LOW. |
Fitted in
- Disk II D3 on the Disk II Interface Card, marked PROM P5
- DuoDisk PROM P5 on the 5.25 controller card
- UniDisk 5.25 PROM P5 on the 5.25 controller card (II/IIe hosts only)
Sources
- MMI 1980 Bipolar LSI Databook, 6308/6309 256 × 8 pin configuration, p. 3-5 (bitsavers)
- MMI 1980 Bipolar LSI Databook, PROM cross-reference (6309 = 74S471; 74S287 = 6301, 256 × 4), p. 3-1
- Apple schematic 050-0005-01, Disk II Interface Card (P5 at D3, Q1/Q2 power switch)
- Understanding the Apple II (Sather), The Bootstrap ROM, p. 9-11
- A2DP: Disk II interface card ROM images (341-0009, 341-0010, 341-0027, 341-0028)