Filter
Top Products
Description
This section describes the microprocessor, connectors, memory
subsystems, and miscellaneous system functions and ports for the
ThinkPad computers.
Microprocessor
The ThinkPad 770 uses the Intel Pentium 200 or 233 MHz
processor with the MMX technology.
The Processor has a 32-bit address bus and a 64-bit data bus. It is
software-compatible with all previous microprocessors. The
Processor has an internal, split data and instruction, 32KB write-back
cache. It includes pipelined math coprocessor functions and
superscalar architecture (two execution units).
Cache Memory Operation
In addition to the 32 KB of internal Level 1 (L1) cache memory in the
microprocessor, the system board of the ThinkPad 770 computer
contains an additional 256 KB of external Level 2 (L2) cache
memory.
The cache memory in the Intel Pentium microprocessor and the L2
external cache memory enable the microprocessor to read
instructions and data much faster than if the microprocessor had to
access system memory. When an instruction is first used or data is
first read or written, it is transferred to the cache memory from main
memory. This enables future accesses to the instructions or data to
occur much faster.
The cache is disabled and empty when the microprocessor comes
out of the reset state. The cache is tested and enabled during the
power-on self-test (POST).
The cache memory in the Intel Pentium microprocessor is loaded
from system memory in 32-byte increments, each referred to as a
cache line
. A cache line is aligned on a paragraph boundary. A
reference to any byte contained in a cache line results in the entire
line being read into the cache memory (if the data was not already in
the cache). When the microprocessor gives up control of the system
bus, the cache memory enters “snoop” mode and monitors all write
2-2 System Board