66 Net finity 3500 -M20 – T ype 8657 Mod els 21 Y, 2 2Y, 31Y, 32Y ,

SCSI port

The server has an integrated dual-channel small computer
system interface (SCSI) controller. This controller supports
an Ultra160 SCSI internal channel. Thi s channel supports
up to 15 SCSI devices. In addition, this controller uses:
• Double-tran sition clockin g to achieve hig h tra nsfer
rates
• Domain name validation to negotiate compatible data
transfer speeds with each device
• Cyclic-redundancy checking (CRC), instead of the
us ual parity checking, to si gnificant ly improve data r eli-
ability
• An active terminator on t he system board for S CSI bus
termination
If you install a SCSI adapter in the se rver, you can use its
SCSI conn ecto r to co nnect diff erent typ es of sma ll compute r
system interface (SCSI) devices.
Note: If you install a PCI RAID adapter, you can move the
SCSI ca ble f r om the sys te m-bo ar d S CSI c onnec t or to
an internal ch annel co nnector on the RAID adapter i f
you want to control t he internal drives from the
adapter.

SCSI cabling requirements

You can install five internal SCSI devices using the SCSI
cable that comes with the server. If you plan to attach exter-
nal SCSI de vices, you must instal l an optio nal SC SI adap ter
and ord er ad ditional SCSI cables. To s elect and order the
corr ect cables for us e with external devices, c ontac t you r
IBM reseller or IBM marketing representative.
For information about the maximum length of SCSI cable
between the terminated ends of the cable, refer to the ANSI
SCSI standards. Adheri ng to these standards will help
ensure that the server operates properl y.

Setting SCSI IDs

Each SCSI device connected to a SCSI controller must have
a unique SCS I ID. This ID enables the SCSI controller to
identify the device and ensure that different devices on the
same SCSI channel do not attempt to transfer data simulta-
neously. SCSI de vices that are connec ted to differen t SCS I
channels can have duplic ate SC SI IDs.
To install external SCSI devices, you must first install an
optional SCSI PCI adapter. Refer to th e information that is
provided with the device for instructions to set its SCSI ID.
3 Ground
4+5 V dc
5Clock
6 No t co nnec te d
Table 10. Auxiliary-device conn ector pin-number
assignments
Pin Signal