UNIBUS priority plug: Difference between revisions
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! Level !! [[DEC part number]] | ! Level !! [[DEC part number]] | ||
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| 4 || | | 4 || 54-08776 | ||
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| 5 || 54-08778 | | 5 || 54-08778 | ||
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| 6 || | | 6 || 54-08780 | ||
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| 7 || | | 7 || 54-08782 | ||
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Revision as of 11:28, 23 February 2024
A UNIBUS priority plug is an insertable plug, physically a DIP, which was inserted into almost all UNIBUS devices in order to select which daisy-chained interrupt bus grant line, of the four such available on the UNIBUS (BG4, BG5, BG6, and BG7), the device's grant-acquiring/passing circuitry was connected to. As a secondary purpose, it passed all the other grant lines past the device.
As part of the configuration of a device being added to a system, it was necessary to ensure that a priority plug for the desired priority level was installed in the device.
Priority plugs were manufactured by DEC for all four priority levels:
| Level | DEC part number |
|---|---|
| 4 | 54-08776 |
| 5 | 54-08778 |
| 6 | 54-08780 |
| 7 | 54-08782 |
Most devices also came with a plug pre-installed at manufacturing time, at a level selected by DEC as likely the most appropriate interrupt priority level for that device; they were rarely changed.
