Rom; 256/640K System Board - IBM XT 5160 Technical Reference

256/640K System Board
The 256/640K system board has either 256K, 512K or 640K of
R/W memory. The memory consists of dynamic 64K by 1 bit
chips in Banks 2 and 3 and dynamic 256K by 1 bit chips in Banks
o
and 1 with an access time of 200ns and a cycle time of 345ns.
All R/W memory is parity-checked.
System Board Minimum Maximum Memory
Pluggable Pluggable
Storage Storage Modu 1
f?;S
(Banks 0-1) (Banks 2-3)
64/256K 64K 256K 64K by 2 Banks 2 Banks
1 bit
of 9 of 9
256/640K
256K
640K 256K by 2 Banks 2 Banks
1 bit
of 9 of 9
and 64K
by 1 bit
ROM
The system board supports both read only memory (ROM) and
R/W memory. It has space for 64K by 8 of ROM or erasable
programmable read-only memory (EPROM). Two module
sockets are provided, each of which can accept a 32K or 8K
device. On the 64/256K system board, one socket has 32K by 8
bits of ROM, the other 8K by 8 bits. On the 256/640K system
board, both sockets have 32K by 8 bits of ROM installed. This
ROM contains the power-on self test, I/O drivers, dot patterns
for 128 characters in graphics mode, and a diskette bootstrap
loader. The ROM is packaged in 28-pin modules and has an
access time and a cycle time of 250ns each.
System Board 1-13