RAMCard Hardware Details

This section describes how RAMCard handles its functions and indicates its States.

The connector cable provides the RAMCard memory chips access to the multiplexed addresses and to a timing signal which is not available through the 50 pin I/O edge-connector.

Addresses for RAMCard memory chips are provided by the Apple motherboard address mux. Data in and out for the single displaced chip (which is U9 on RAMCard) are routed through the connector cable. Data in and out for the other eight chips on RAMCard (in sockets U1- U8) are routed through the I/O edge-connector. The data out from the chips in sockets U1-U8 are buffered on RAMCard (by the ICs in sockets U19 and U20) to ensure sufficient drive capability. Control addresses and status information are routed through the I/O edge-connector.

The decoding of the addresses and the storage of the state for each function are performed by the ICs in sockets U14-U18. The IC in socket U13 drives the LED indicators. Part of the IC in socket U19 buffers and selects the status bits during function selection. Once the state of each function is selected, the memory accesses on RAMCard are controlled by the ICs in sockets U ll, U12, U l5, and U18.

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