ECS NEATSX User Manual page 17

Notice that there are two sizes of RAM chips; 256 Kbit, and 1
Mbit. It is important to distinguish between bits and bytes here. The
bit measurement is for individual chips; the byte measurement is for
total memory size for a set of nine chips.
All the RAM chips function in sets of nine whether they are
installed individually or are part of a module. The individual chip
measurement, e.g., 256 Kbit, represents the total amount of memory in
one chip. Eight chips for memory plus one for parity checking make
up a set of nine.
A set of nine 256 Kbit chips or their equivalent will therefore
total 256 kilobytes of memory. The configuration of two 44256 chips
and one 41256 chip noted previously is equal to the configuration of
nine 256 Kbit chips. Both have a total memory of 256KB. One 44256
chip has the memory capacity of four 41256 chips. Nine 1 Mbit chips
will equal one megabyte of memory. Each DIP RAM bank on the
NEATsx has two sets of nine sockets. The figure on the next page
shows the socket configuration of the DIP RAM banks.
SIP modules come in two memory capacities: 256KB or 1MB
per module. One SIP module is equivalent to nine DRAM chips. Two
modules, therefore, are necessary for one memory bank.
Hardware Specifications
11