IBM1S506.ADD
is the IBM driver which is shipped with &os2;.
IBM has updated this driver quite a number of times. A newer driver is required
for OS/2 Warp 3 and 4 if you wish to use hard disks which are larger than 8 MB.
With this driver, many of the dialog items are disabled because they are
only used with DANIS506.ADD
(below).
DANIS506.ADD
is a replacement driver written by Daniela Engert.
It is 99% command-line compatible with the IBM driver, but has added lots of
enhancements. Since the IBM drivers cannot enable busmastering
support with many of the newer chipsets, it is strongly recommended to use this
enhanced driver, which can greatly enhance hard disk performance. Also, this driver
allows to to configure your hard disk controllers in much more detail to resolve
problems with your system setups.
It is however necessary to understand in general that both drivers differentiate between three type of options:
DANIS506.ADD
) how hardware is searched at bootup.
With both the IBM1S506.ADD
and the DANIS506.ADD
drivers,
adapter settings must be specified only after an /A:x
option, with
x
specifying the adapter to be configured by all the following
options (either 0 or 1). The dialog will add this option automatically if you
change any adapter parameter from a non-default value. All the settings in the
"Adapter (controller) settings" group therefore affect only the adapter
which is currently selected in the "Current adapter" group.
Each adapter needs a few system resources such as an interrupt (IRQ), a Direct Memory Access (DMA) channel, and port addresses (base address) for data interchange between the adapter and the computer. If these options are not set, the driver uses defaults which work on most systems.
See the remarks below for details about bus-mastering (DMA) support.
With both the IBM1S506.ADD
and the DANIS506.ADD
drivers,
unit settings must be specified only after an /A:x
option first
(which specifies the adapter) and a /U:x
option next (which specifies
the unit in the adapter), with x
being 0 or 1 each time.
The dialog will add these options automatically if you
change any unit parameter from a non-default value. All the settings in the
"Unit (drive) settings" group therefore affect only the unit
which is currently selected in the "Current unit" group.
While the older Programmed I/O (PIO) modes 3 and 4 still required control by the
main processor, the EIDE standard introduced several multi-word DMA modes. In those
modes, the drive takes over control of the bus (bus-mastering) and places data
directly into the main memory (DMA). The standard IBM1S506.ADD
fails
to recognize many chipsets and can thus not enable busmastering on many systems.
DANIS506.ADD
does a much better job at this and still allows you to
fine-tune the detection process.
Ultra-DMA is yet another extension of the original DMA protocol. Previously, data transfers took place only on the rising edge of the strobe signal. Ultra DMA modifies the protocol to allow data to be sent on the falling edge of the strobe signal as well, thus doubling the data transfer rate. Also, because of the increased danger of data corruption, error detection was added. As a result, Ultra-DMA is both faster and safer than regular DMA or plain PIO.
DMA with hard disks can cause problems on some hardware however. This can be due to
older controller hardware which cannot handle this at all, or bad cables which
cause too much noise on the bus so data is corrupted at higher speed.
Also, many older drives cannot handle DMA well or only at lower speed.
For this reason, busmastering can be disabled
totally or (with DANIS506.ADD
) limited to a fixed data rate.
The adapter /BM
setting enables or disables busmastering for
a whole adapter (that is, both units which are connected to that adapter). This
option has been available in all versions of IBM1S506.ADD
and is
supported by DANIS506.ADD
as well.
The unit /BM
setting enables or disables busmastering for
one unit only. This option is only available in newer versions of IBM1S506.ADD
and is supported by DANIS506.ADD
as well.
With DANIS506.ADD
, you can also limit the data rate for a certain
unit by explicitly specifying the protocol to use.