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Description:Check if your HD setup is 4GB-ready.
Developer:Thomas Rapp
Short: Check if your HD setup is 4GB-ready
Uploader: thomas-rapp@web.de (Thomas Rapp)
Author: thomas-rapp@web.de (Thomas Rapp)
Type: disk/misc
Version: 1.6
Architecture: m68k-amigaos >= 2.0.4

New in this release

- TD64 test didn't work in all cases
- SCSI test didn't work
- version information about FFS in check4gb.filesys was wrong
- output "ok?" instead of "ok" for drives larger than 128 GB.


Amiga Computers with Kickstart 3.1 and below cannot handle hard drives
greater than 4GB. Although there are many solutions and even OS3.5+ claim
to be compatible with large hard drives, it is sometimes difficult to be


The standard interface between a device driver (e.g. scsi.device) and a
file system (e.g. FastFileSystem) addresses blocks on a drive by a 32 bit
address. With 32 bits you can address 2^32 bytes = 4GB.

There are three solutions to expand this border:

- TD64 is a 64 bit command set invented by Phase5 and other third-party

- NSD is a new style to communicate with a device driver. It also adds 64
bit commands similar to TD64.

- Direct-SCSI is a method to send raw device commands directly to the SCSI
bus. Most IDE drivers understand and emulate these commands, too.

To bypass the 4GB border you need a device driver and a file system that
both support the same command set out of the above.


The program can be run from a Shell window or from the Workbench. When run
from Workbench or without Shell parameters, the GUI opens.

It checks every partition that is mounted in the system if it resides above
the 4GB border or overlaps it, and if yes, compares the command sets
available with those supported by the file system used.

The window lists all partitions found along with the informations inquired.
The last column is the most important: it reads either "ok" or "***". If it
is ***, this partition must not be used ! After the *** the command sets
supported by the device driver are listed.

If the last column is "ok?" this means that the partition lies partially
above the 128 GB border. Check4GB is not yet able to test if a device is
IDE or SCSI and if IDE if it supports LBA 48 for drivers larger than 128


It is not possible to test which command set a file system uses. Because of
this, Check4GB needs a configuration file that lists the file systems along
with the supported command sets.

The configuration file is called check4gb.filesys and is searched in the
current directory, in Check4GB's program directory and in S:.

Every file system not listed in the configuration file is considered to not
support any of the new command sets.

The config file looks as follows:

<filesystem> <version> <command set 1> <set 2> <set 3> <comment>

One line for each file system.

filesystem the first three characters of the DosType. E.g. if the
DosType is 444f5303 (DOS\3) the filesystem column is DOS.

version the lowest version that supports the listed command sets.
If the same file system is listed multiple times with
different version numbers, the higher versions must apear
before the lower ones.

command set Up to three command sets this file system supports. Options
are one of TD64, NSD and SCSI.

comment Everything after the third command set is ignored.

The example check4gb.filesys contains all modern file systems that I know.

Shell Parameters

When started from the Shell with parameters, it can test either one DOS
device or an Exec device driver.

Usage: check4gb <drive|device> [unit]

Examples: check4gb scsi.device 0
check4gb scsi.device
check4gb dh0:

Parameters: drive The name of the DOS device to test.

device The name of the Exec device driver of your hard drive.

unit The unit number (or SCSI id) of your hard drive.
If no unit is given, all units of <device> are checked.

Output: xxx.device unit y supports NSD commands
xxx.device unit y supports TD64 commands
xxx.device unit y supports SCSI-Direct commands
xxx.device unit y does not support harddisks larger than 4GB

Self explaning, I hope

cannot open xxx.device unit y

The device/unit combination you specified is invalid.


This program was only tested on my machine with my harddisks. There is no
guarantee that it runs on others. I am not responsible for any damage. Use
them on your own risk.

Upload Date:Aug 20 2017
Size:19 KB