Cromemco 16K Dynamic RAM Board  
Cromemco almost from the start decided to build their systems with dynamic RAM memory cards. They started with this 16K card. It was produced with minor modifications for many years.

The card had a bank select feature allowing up to 8 banks to reside in one system. Active banks could be selected in software -- ideal for multiuser systems and CPM3 by outputting the appropriate bit to port 40H.  Each board had an LED indicating when it was active. The board also could handle DMA but did not have its own onboard memory refresh controller. Refresh was done during the 8080 or Z80 M1 cycle.  Not sure it would work in more complex master/slave systems. As with the Vector Graphic boards without an LSI refresh controller special care had to be taken with the POC/RESET lines that the signal times were short (see manual below). The card worked at up to 4MHz with no wait states.
 
The manual for this board can be obtained here.