IBM PS/2 90 XP 486 Hardware Maintenance Reference page 14

2.3.1 Processor Boards
The functions of the system can be significantly changed depending on
which processor board is installed.
All processor boards plug into the system board through two dedicated
in-line connectors. The major components on the processor board are:
System microprocessor
System clock
Direct memory access (DMA) controller
Memory controller.
Note: Some processor boards have a connector for an optional 256KB cache.
The processor boards fall into one of three types (type 1, 2 or 3)
depending on the following:
Type of DMA controller installed (16 or 32-bit)
Type of memory error detection supported (ECC or parity)
Type of memory configurations supported (interleaved or
noninterleaved).
For more information, see "System Memory" in topic 2.4.
The microprocessors used are 32-bit.
virtual-address (protected) mode.
clock speed varies within each type of processor board.
IBM PS/2 Model 90 XP 486 and 95 XP 486 HMR
Processor Boards
They operate in the real-address or
The amount of memory supported and the
¦ Copyright IBM Corp. 1990, 1992
2.3.1 - 1