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includes
address
protection mechanism to support operating systems.
code compatible with 8086 family of microprocessor.
features
to
support
non-maskable).
It has two modes of operation: Real address mode and Protected
virtual address mode.
In real address mode it operates as a fast 8086 with 32-bit extension if
desired.
In Protected mode, software can perform a task switch into tasks
designated as virtual 8086 mode tasks.
and protected from one another by the use of paging and I/O permission bit map.
3.2 System Performance
Clock Speed
The AMI-386SX operates at 16 MHz, which results in a clock cycle time of 62.5
ns.
It can run at two different speeds.
The lower speed is equivalent to a clock speed of 8MHz. For convenience, we
shall assume this speed to be 8 MHz throughout the rest of this manual.
The panel-mounted turbo switch determines the initial speed after power-on.
The speed can be switched at any time while the machine is operating.
If
installed
the
frequency.
Data Access: Bus Width
The
80386SX
microprocessor
Input/Output.
Each type of access can be 16- or 8-bit wide.
I/O devices are 16 or 8 bit wide.
device of any width.
into a number of (upto 16 / 8 = 2) cycles to allow access to a 16- or 8-bit
device.
All the on-board devices in the memory space is organized 16-bit wide.
These include the on-board DRAM and the EPROM containing the BIOS.
on-board I/O devices are 8-bit wide, with the exception of the 80387SX math
coprocessor which is a 16-bit device.
The AMI-386SX can support 16- and 8-bit memory and I/O devices on the I/O
slots.
EGA/VGA RAM Shadow
The memory space from address 0C0000 thru 0DFFFF is reserved for I/O slot ROM.
Most often, only the EGA BIOS (0C0000-0C3FFF), which is accessed through a
translation
registers,
coprocessors,
80387SX
Numeric
supports
If necessary, the hardware will split a 80386SX bus cycle
advanced
DMA
and
interrupts
The virtual 8086 tasks can be isolated
processor
runs
two
types
The AMI-386SX allows any type of access to a
multitasking
hardware
In addition, it is object
The 80386SX has built-in
(both
maskable
at
the
processor
of
accesses:
Memory,
The memory and
and
and
clock
and
All the
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