Ampro Corporation P5X manual System Memory, Shadowing, Memory Address Function

Little Board/P5x Technical Manual

System Memory

The module supports a single standard 64-bit DIMM position (168-pin) for the 64-bit data path to the Pentium processor. Both EDO and SDRAM memory types are supported. Buffered DRAM is not supported. You can install from 16M bytes to 256M bytes, depending on your memory needs.

The ROM BIOS automatically detects the size of the installed memory module and configures the system accordingly at boot time. (No jumpering or manual configuration is required.) The amount of memory the BIOS measured can be displayed by running Setup.

You can use EDO DRAMs or SDRAMS with access times of 60 nS or less.

Memory parity and error correction (ECC) are not supported by the chip set used on the Little Board/P5x.

DRAM memory is allocated in the system as shown in Table 2– 7.

Table 2– 7. System Memory Map

Memory Address	Function
FE0000h - FFFFFFh	Duplicates BIOS at 0E0000-0FFFFFh.
100000h - FDFFFFh	Extended memory
0E0000h - 0FFFFFh	128K ROM BIOS
0D0000h - 0DFFFFh	BIOS extension option, if enabled. Otherwise, free.
0CB000h - 0CFFFFh	USB
0C0000h - 0CAFFFh	Video BIOS (44K)
0A0000h - 0BFFFFh	Normally contains video RAM, as follows:
	CGA Video: B8000-BFFFFh
	Monochrome: B0000-B7FFFh
	EGA and VGA video: A0000-AFFFFh
000000h - 09FFFFh	Lower 640K DRAM

ROM BIOS

The standard BIOS is installed in a 256K byte Flash device at the factory. The top 128K bytes of the Flash device is reserved for the system BIOS, located at 000E0000h – 000FFFFFh and mirrored at the top of the memory address space. The remaining 128K bytes are mapped only to the top of memory.

A utility program, PGM5X.COM, can be used to program the on-board Flash device. It can be used to update the system BIOS, video BIOS, SCSI BIOS, or user area. The utility is included on the utility diskette that accompanies the Ampro Development Platform. The diskette includes documentation about how to use the program.

Shadowing

To improve system performance, the contents of the ROM BIOS and video BIOS are copied into DRAM for execution (“shadowed”), where they are accessed as 64-bit wide data. Shadowing a BIOS

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