ICP GDT6618RD, Addendum

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You can access the change SCSI Parameters / Initialize menu by clicking the right mouse
button on a Physical Drive in the Physical Drives Windows (View
> Physical Configuration)
Synchronous Transfer
Different to the older asynchronous transfer mode, the synchronous transfer offers higher
transfer rates on the SCSI bus. The maximum synchronous data transfer rate depends on
the width of the SCSI bus (8 bit narrow SCSI, 16 bit wide SCSI) and the frequency of the
signals on the SCSI bus (10 MHz for Fast SCSI, 20 MHz for Ultra SCSI and 40 MHz for Ultra2
SCSI and Ultra 160 SCSI). The maximum data transfer rates are:
Narrow SCSI (8Bit) Wide SCSI (16Bit)
Fast SCSI
10 MB/s 20 MB/s
Ultra SCSI
20 MB/s 40 MB/s
Ultra2 SCSI
- 80 MB/s (LVD SCSI ( l ow v oltage
d ifferential) only)
Ultra 160
- 160 MB/s (LVD SCSI ( l ow v oltage
d ifferential) only)
Note: The maximum synchronous data transfer rate between a SCSI device and the ICP
Controller can be limited. This limitation may become necessary if a particular SCSI cabling
does not allow the maximum rate the controller and the drive could achieve. The adjust-
ment of the synchronous transfer rate can be done in the SCSI parameters / Initialize menu.
Notes: In order to select a transfer rate above 10 MB/s the protocol has to be set to SCSI-III.
Higher frequencies (single ended SCSI) require better cabling, shorter cables and a profes-
sional termination of the SCSI bus.
Disconnect
This SCSI feature enables a SCSI device to disconnect from the SCSI bus. By releasing the
SCSI bus while the device doesn’t need it, the bus becomes free for other devices to trans-
fer or receive data. An example for a disconnect situation is a hard disk that needs time to
read data from its media after receiving a read command. It may then disconnect from the
SCSI bus so that other devices can transfer data. Later on it reconnects when it is able to
deliver the data instantly. You can change the disconnect setting for a hard disk in the SCSI
parameters / Initialize menu.
Tagged Queues
This feature enables modern hard disk drives to receive several commands at one time and
then process them in an optimized order. Few, mainly older drives, do not or not correctly
support this feature. You can change the tagged queues setting for a hard disk in the SCSI
parameters / Initialize menu.
SCSI read cache / SCSI write cache
These settings enable or disable the write and read caches of the hard disks. Turning these
caches off degrades the performance of the hard disk. You can change the cache settings of
a drive in the SCSI parameters / Initialize menu.