Processor; Clock Mode; Sleep Mode - Toshiba T2200SX User Manual

2.2 Processor

The T2200SX CPU is an Intel 80386SX-20 microprocessor. The 80386SX operates in both, real
and protected modes. Real mode can only directly access 1MB of memory. The architecture is the
same as the 8086, but allows access to the 32-bit register set of the 80386SX. The protected mode
allows the 80386SX to increases the linear address space to access four gigabytes. This allows the
virtual memory to run programs of almost unlimited size. Virtual Memory management is based on
segmentation, four levels of protection, and an optional paging mechanism. For the details about the
80386SX hardware and its instruction set, refer to the Intel 80386SX Hardware Reference Manual
and Programmer's Reference Manual.

2.2.1 Clock Mode

The 80386SX processor can operate at clock rates of 20MHz (high speed) and 10 MHz (low speed).
To switch between the two rates, hold down the Fn key, and press the PgDn key to select slow
speed; pressing the Fn and PgUp keys returns the processor to high speed. The slow speed may be
required by some software packages.

2.2.2 Sleep Mode

The 80386SX processor sleep function is executed by the HALT command from the CPU. When
the CPU executes the HALT command, the clock speed reduces to 5MHz to save power.
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