Ampro Corporation 486E manual Dram, System Memory Map

Product Reference

DRAM

There is no DRAM soldered on board. The Little Board/486e CPU will support up to 64M byte of system DRAM. A single vertical 168-pin DIMM socket supporting symmetrical EDO 3.3V modules is used.

When the system boots, the BIOS measures the amount of memory installed and configures the internal memory controller. No jumpering or manual configuration is required. The amount of memory found can be displayed by running SETUP. Saving SETUP automatically stores this figure in the Configuration Memory.

Note

If you change the amount of memory installed, you must run SETUP again to save the new value in the Configuration Memory.

Onboard 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 the top 64K to shadow the ROM BIOS. DRAM can also be mapped into a portion of this region to shadow a video BIOS (a SETUP option).

!The remaining memory is mapped to extended memory starting at the 1M byte boundary.

System Memory Map

The Little Board/486e CPU address up to 64M bytes of memory. Table 2–6 shows how this memory is used.

The first megabyte stores the following data starting at memory address 00000h:

!DRAM

!Byte-wide socket

!ROM BIOS

2–9