Offered here is a Macrotech International Corp high density RAM board for the S-100 bus, a high capacity 512k expansion card from the later era of S-100 computing. 

The board has D4164C-12, which are 64K x 1, making this a 512KB board.

It is clearly intended for banked operation and use in disk-centric, multi-user, or memory-intensive S-100 environments such as MP/M systems, RAM disks, or specialized industrial or institutional applications. The board is populated with DRAM devices and associated control logic. 

This board represents a significant leap beyond earlier 8K and 16K cards, reflecting the transition to higher density 120 nsec dynmaic memory designs used in advanced Z80 and multiuser S-100 systems. Boards of this size were typically used in more sophisticated setups running CP M or similar operating environments requiring expanded memory. It also had a LSI dynamic RAM controller that Macrotech stated made the board look like static RAM

Macrotech International boards are not commonly encountered, and S-100 memory cards like this are increasingly sought after for advanced builds and serious collections.

This board is compatible with S-100 systems such as the Altair 8800 and IMSAI 8080, as well as later S-100 machines designed to support extended memory.

Condition
Clean vintage condition
Board appears complete
Components appear original
Not recently tested 

Sold as is due to age.

Features
Macrotech International Corp S-100 memory board
512k high capacity RAM
Late era S-100 design
Designed for advanced Z80 and multiuser systems
Significantly higher density than early S-100 memory boards
S-100 bus compatible

Notes
Vintage electronics sold as is
Untested beyond visual inspection
May require configuration, documentation, or restoration before use
Compatibility with early systems may require additional hardware or configuration