RH750 Massbus Adapter
From Computer History Wiki
The RH750 Massbus Adapter was a MASSBUS device controller for the VAX-11/750's CPU Memory Interconnect (CMI).
It was implemented on one extended hex card, which mounts in the VAX-11/750 backplane in one of the three CMI option slots.
A VAX-11/750 could have up to three RH750 Adapters, the first one goes into CMI slot 9, the second into slot 8, and the third in slot 7.
It was common practice to have two separate RH750s, one for tape and another for disk devices. Combining both on one RH750 was possible, but tape usage had a negative impact on disk performance.
CMI Option Slot Configuration Rules
CMI option slots can be used for other adapters, too:
Allowable Configurations of CMI Slots 7, 8, & 9:
| Slot 7 | Slot 8 | Slot 9 |
|---|---|---|
| RH750 | RH750 | RH750 |
| DW750 | RH750 | RH750 |
| DR750 | RH750 | RH750 |
| DW750 | DR750 | RH750 |
| DW750 | CI750 | RH750 |
| CI750 | RH750 | RH750 |
NOTES:
- Combination of DR750 and CI750 is not allowed
- Only one DR750 per system is allowed
- Only one DW750 per system is allowed
- Only one CI750 per system is allowed
See also
- RH750 Massbus Adapter Technical Description (EK-RH750-TD) - not available online
External links
- RH750 Field Maintenance Print Set (MP-01045)
