Specifications
Hardware Configuration
2–9
Note
Some memory modules are “taller” than others. The tall SIMMs
will increase the thickness dimension of the Little Board/P5.
On-board memory is allocated as follows (standard for the PC architecture):
The first 640K bytes of DRAM are assigned to the DOS region 00000h to 9FFFFh.
DRAM in the top 384K bytes of the first 1M byte is not available for user programs. DRAM is
mapped into this area to shadow the ROM BIOS, video BIOS, and PCI drivers. (Shadowing is
described in the following section.)
The remaining memory is mapped to extended memory starting at the 1M byte boundary.
A more detailed memory map is provided in Chapter 3.
When the system boots, the BIOS measures the amount of memory installed and configures the internal
memory controller for that amount. (No jumpering or manual configuration is required.) The amount it
measured can be displayed by running SETUP.
2.3.1 Shadowing
To improve system performance, the ROM BIOS and video BIOS are shadowed. When the system
operates directly from ROM code, it accesses an 8-bit memory device. When the ROM contents are
shadowed, the contents are copied into system DRAM where they are accessed as 64-bit wide data.
Shadowing a BIOS ROM substantially enhances system performance, especially when an application or
operating system repeatedly accesses the ROM. Shadowing for both the ROM BIOS and the video BIOS
is built into the Ampro Extended BIOS. There is no user setting.
2.3.2 Expanded Memory and Extended Memory
Memory above the 1 megabyte boundary is called “extended” memory. It is a contiguous linear block of
memory. Some programs require that memory be available as EMS memory. The EMS memory standard
makes memory available as pages rather than as a contiguous block. The exact manner for accessing
EMS memory is defined in the LIM 4.0 specification.
You can convert the board’s extended memory into expanded memory using DOS EMS emulation
utilities. Current versions of DOS provide EMS emulation utilities that conform to the LIM 4.0
specification. Refer to your DOS technical documentation for instructions for using their EMS emulation
utility.
2.4 MATH COPROCESSOR
The Pentium CPU contains a built-in floating point math coprocessor. There are no configuration
jumpers or options for the math coprocessor.
2.5 SERIAL PORTS
The Little Board/P5i provides four standard RS232C serial ports, Serial 1 and Serial 2 at J11, and Serial
3 and Serial 4 at J13.