National Semiconductor NS23M QBUS memory
From Computer History Wiki
The National Semiconductor NS23M is a QBUS memory card in dual QBUS card-size format, with a maximum capacity of 256 Kbyte (using 64Kx1 DRAMs).
Configuration
The board is configured with a combination of jumpers and DIP switches.
| Jumper(s) | Function |
|---|---|
| W1-W2, W17-W18 | 200ns/150ns DRAM |
| W3-W4 | Test |
| W5-W7, W12 | 16K/32K/64K DRAM |
| W8-W9 | Test |
| W10-W11 | Internal/External Refresh |
| W13-W14 | 32K DRAM Upper/Lower |
| W15 | 18-/22-bit QBUS (in/out) |
| W16 | External Refresh / MEMSEL |
| W19-W20 | Battery Backup |
Starting Address
| Switch | Address bit |
|---|---|
| S1-1 | 20000 |
| S1-2 | 40000 |
| S1-3 | 100000 |
| S1-4 | 200000 |
| S1-5 | 400000 |
| S1-6 | 1000000 |
| S1-7 | 2000000 |
| S1-8 | 4000000 |
| S1-9 | 10000000 |
Size
| Jumper(s) | Function |
|---|---|
| S2-1 | 16KB |
| S2-2 | 32KB |
| S2-3 | 64KB |
| S2-4 | 128KB |
| S1-10 | 2K/4K I/O Address Space (closed/open) |
Note that the size is the value indicated, plus 16KB (the minimum); i.e. 0000 = 16KB, 1111 = 256KB.
