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RAMCard Hardware Details
This section describes how RAMCard handles its functions and indi-
cates 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 sock-
ets U19 and U20) to ensure sufficient drive capability. Control address-
es 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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