REV11 DMA Refresh/Bootstrap/Terminator
The REV11 DMA Refresh/Bootstrap/Terminator is a QBUS card which contains several different functions:
The 'refresh' capability is because the earliest QBUS DRAM main memory cards (such as the MSV11-B) did not have 'on board' refresh capability, but depended on external refresh, performed over the QBUS. That refresh could be performed either by the LSI-11 CPU, or an external device, such as the REV11 (if so, a jumper on the LSI-11 would disable it from doing refresh).
The REV11 comes in two forms: the REV11-A (M9400-YA) contains all three functions listed above; the REV11-C (M9400-YC) omits the 120-ohm terminators.
The REV11 is a dual card. It is one of three different peripherals which can be produced from the same PCB (DEC part number 50-11903B), depending on exactly which components are inserted into the card. The others are the TEV11 Terminator and the M9400 expansion cable connector card.