Specifications

Hardware Configuration
2–27
Figure 2–7 Using 28-pin Devices in a 32-pin Socket
2.10.1 Addressing the Byte-Wide Socket
Use SETUP (described in Chapter 3) to enable or disable the socket, and specify whether the byte-wide
socket or the OEM Flash device is enabled by the BIOS upon system initialization.
Byte-Wide Socket Address
When enabled, the byte-wide socket resides in a 64K contiguous block starting a D0000h.
Note
When a 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.
The size of the device installed in the byte-wide socket is not limited to 64K bytes. Using a page
addressing scheme, devices (or modules) up to 1M bytes can be used. The upper address lines
(A16-A19) are synthesized and can be set by software. A description and examples of byte-wide page
control are provided in Chapter 3.
If a device larger than 64K bytes is installed, you must select which page is visible in the address
window. A page is 64K bytes. The Ampro Extended BIOS provides convenient software calls to manage
enabling/disabling the socket and selecting pages. Refer to Chapter 3 for details about the byte-wide
extended ROM-BIOS calls.
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 will see two copies of a
32K device in a 64K window.
ROM-BIOS Extensions
The system can be configured to run its application from the byte-wide socket instead of loading it into
DRAM 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. The
ROM-BIOS extension concept, and its practical implementation, is discussed in Ampro Application
Notes AAN-8702 and AAN-9003.
Performance Issues
Note that executing programs directly from the byte-wide socket can adversely affect system
performance. There are a number of factors that can contribute to the performance impact: