DSP 104-plus, Reference Manual

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these operating systems. This situation may change in the future, so contact us if you
have an interest in these operating systems.
6.6.1 Overview
The ability to operate without mechanical disk drives is a key feature of the TP400.
To do this you can make use of the Flash File System (FFS) that is provided with
every TP400. As well as being more robust than mechanical drives they are also
faster, at least for read operations.
The FFS provided with the TP400 is the FlashFX product from Datalight Inc. DSP
Design have paid a license fee for every standard TP400, so you may use the Flash
File System on every standard TP400 you buy. (Some volume users who do not
require the FFS may ask for TP400 boards without the license, to reduce costs).
The Flash File System driver is implemented as a BIOS extension or as a loadable
device driver. In order to boot the operating system from the Flash File System disk
drive the BIOS Extension option must be chosen, as a loadable device driver can
only be loaded after DOS has booted from another disk (such as a floppy disk).
However, the loadable device driver option can be used when another device (an IDE
drive for instance) is the boot device. The loadable device driver is also required
during the initial formatting of the Flash disk.
The Flash File System driver is normally implemented as a BIOS extension. This
driver must be programmed into the Flash memory, and then it is located every time
the TP400 boots. The standard TP400 is shipped with the FFS device driver already
present in the Flash memory as a BIOS extension and it can be enabled or disabled
in the Setup program, using the Main menu. By default the FFS BIOS extension is
disabled in the Setup program.
The loadable device driver requires the driver to be placed on the boot disk, and it is
activated by an appropriate entry in the CONFIG.SYS file.
In normal use you should use either the BIOS extension or the loadable device driver
- not both. The only time it is permissible to use both is during initial formatting as
explained in section 6.6.2.
In either case, the FFS driver operates by intercepting calls to the BIOS disk drive
sub-system, which uses software interrupt INT13. Calls that are not intended for the
FFS are passed through to the BIOS. Calls that are intended for the FFS are
performed by the FFS driver.
The FFS BIOS extension requires 16k bytes of memory, from CC000H - CFFFFH. A
small amount of RAM within the 640k bytes available to MS-DOS is also used by the
FFS. When accessing the Flash memory chip, the FFS driver software does so at
memory addresses E0000h - E7FFFh.
The Flash File System is designed for MS-DOS and related operating systems. It is
likely that the Flash File System BIOS extension will not operate with some other
operating systems, and may need to be disabled.
The Flash File System driver will cause the Windows 95 disk system to run slowly.
This is because when the Flash File System is installed Windows 95 uses the 16-bit
DOS file system, rather than its faster 32-bit native file system. It is unlikely that