Ampro Corporation 486E manual Addressing the Byte-wide Socket, Window Address, ROM-BIOS Extensions

Product Reference

Addressing the Byte-wide Socket

Use SETUP to specify the size and starting address of the byte-wide socket, and whether the BIOS enables the socket upon system initialization. Table 2–36 lists the possible settings for sizes and address ranges of the byte-wide socket.

Note

When the byte-wide socket is enabled, the memory address space it uses is unavailable for other devices, even if no memory device is installed in the socket. You must disable the byte-wide socket in SETUP before you can use the memory space for other purposes.

Table 2–36. Window Size and Address Selection

Window	Address
DISABLE	N/A
64K	D0000-DFFFFh
64K	E0000-EFFFFh
128K	D0000-EFFFFh

A device used in the byte-wide socket must have access times of 250 nS or less.

If you install a device that is smaller than the selected window size, the contents of the device are duplicated in the byte-wide socket’s memory space. For example, the software sees two copies of a 32K device in a 64K window, and 4 copies in a 128K window.

A16 is inverted so 128K devices programmed off board will have the halves swapped, for example, the lower half will be in the E0000 segment.

ROM-BIOS Extensions

The system can be configured to run its application from the byte-wide socket instead of loading it from a disk drive. This technique, known as a ROM BIOS extension, directly executes the application during the Power-On Self Test (POST) instead of booting from floppy or hard disk. For additional information regarding the ROM-BIOS extension concept and its practical implementation, contact Ampro Technical Support.

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