View source for REV11 DMA Refresh/Bootstrap/Terminator

The '''REV11 DMA Refresh/Bootstrap/Terminator''' is a [[QBUS]] card which contains several different functions:

* [[Dynamic RAM]] [[main memory]] [[memory refresh|refresh]]
* [[Read-only memory|ROM]] memory for [[bootstrap]]ping
* 120-ohm [[bus]] [[terminator]]s

The 'refresh' capability is because the earliest QBUS DRAM main memory cards (such as the [[MSV11-B MOS memory|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]] [[Central Processing Unit|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 [[DEC card form factor‎|dual]] card. It is one of three different  [[peripheral]]s which can be produced from the same [[printed circuit board|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]].

==External links==

* [http://www.bitsavers.org/pdf/dec/qbus/Digital_Microcomputer_Interfaces_Handbook_1980.pdf microcomputer interfaces handbook] - the REV11 is covered on pp. 538-546 (pp. 546-554 of the PDF)
* [http://bitsavers.org/pdf/dec/qbus/MP00706-ET-LSI-11_Dec81.pdf ET-LSI-11 Field Maintenance Print Set] (MP00706) -  the REV11 is covered on pp. 241-246 of the PDF

[[Category: QBUS]]
[[Category: QBUS ROMs]]