Ampro Corporation 486E - Manual (Page 66)

Little Board™/486e Technical Manual
2–50
Performance Issues
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:
! The byte-wide device is substantially slower than DRAM, as it is an 8-bit device instead of 32-
bit device.
! The device is accessed from the PC expansion bus, which is much slower than the high-speed
processor memory bus.
Performance can be substantially improved by copying the contents of the byte-wide device into
RAM and executing directly from RAM.
Solid State Disk (SSD) Drives
Using the Ampro Solid State Disk (SSD) Support Software, you can configure EPROM, Flash
EPROM, or SRAM solid-state devices, installed in the byte-wide sockets, to act as one or more disk
drives. No custom programming is required. Regular DOS-compliant programs, including standard
DOS utilities, can be used without modification.
Ampro’s SSD support software creates data image files, based on your application programs and
operating system, which can be programmed into the devices you install in the byte-wide sockets.
The Ampro ROM-BIOS treats these devices like one or more disk drives, loading the programs into
DRAM for execution. The sockets can be combined to serve as a single drive, or each socket can be
used as a separate drive. You can use SSD drives in addition to, or instead of, normal floppy and
hard disk drives.
You can increase system SSD capacity by adding one or more of Ampro’s SSD expansion modules.
Accessing the Byte-Wide Socket
To access the byte-wide socket, it must be enabled. Using SETUP, either device can be enabled at
boot time. This places the contents of the enabled device at the address specified in SETUP and the
processor can access this memory in a normal fashion.
Here is a simple assembly language routine showing how to use an Ampro extended-BIOS call to
enable or disable the byte-wide memory socket, S0. This code selects the first 64K page on large
devices.
;----------------------------------------------------------
; Access control code for a byte-wide socket
;----------------------------------------------------------
MOV AH,0CDH ; AMPRO function call
MOV AL,03h ; Use 03 for S0
MOV BL,nn ; Use 01 to turn ON or 00 to turn OFF
MOV BH,00 ; Selects page 0 of the device
INT 13H
Table 2–37 lists the segment addressing in large memory devices.