Where is scsi located

All devices on the bus must have unique target addresses. The addresses for the internal CD-ROM and tape drives are determined by jumpers located on the drives. If the CD-ROM and tape drives have been factory-installed, they are configured with the correct addresses for the system. When installing an internal CD-ROM or tape drive as an option, you should verify the address settings on these devices.

The settings usually involve three sets of pins that determine the address in binary. Attaching a jumper across a set of pins creates a binary 1 in that position. See the documentation accompanying the drive for device-specific information about checking and setting jumpers. You must include the Enterprise internal bus length 0. Use the following cabling guidelines to ensure proper device cabling and termination on the external SCSI bus:.

Many systems have built-in SCSI support, and you would not need to install any additional cards. If you need to install a SCSI controller card, and it is either an SBus card or a PCI card, the card will be logically addressed automatically based on the order and connector that it is plugged into.

Address selection schemes for disk drives differ from address selection schemes for tape drives. This section discusses the SCSI address selection schemes for different types of peripheral devices. Addresses and Device Names The Solaris software identifies a peripheral through a series of addresses and device names:.

Target ID address - an address that is set on the interface of the device by you or by the installer. Physical device name - assigned by the system firmware based on its physical connection to the system. Logical device name - assigned by the operating system when the peripheral is installed. There are three methods to set this address:. Jumpers - an address is achieved by placing jumpers on shunts. If your device requires jumper installation, consult the documentation that shipped with your device.

Switch - used when a device is in an external enclosure an enclosure other than the system chassis. The enclosure provides a switch that you set to your desired target ID address. Single-connector - a device with a single connector receives data, power, and address information through the same connector.

This sort of device is automatically addressed when you install it. This is the most common method of addressing Sun disk drives. Determining the correct target ID for your device depends on several conditions:.

Device type - some device types, such as CD-ROM and tape drives, are most easily identified by the operating system when they use certain addresses. See the table below:. If 15 devices are connected, valid disk target IDs are Physical Device Names The physical device name is assigned by the system firmware. This name is expressed in the form of a path name. For more information on and fault tolerance, check out this page. The chart on this page compares several of them. Many of the slower ones are no longer in use -- we've included them for comparison.

In addition to the increased bus speed, Ultra SCSI uses packeted data transfer, increasing its efficiency. Ultra2 was also the last type to have a "narrow," or 8-bit, bus width. All of these SCSI types are parallel -- bits of data move through the bus simultaneously rather than one at a time.

SAS uses a point-to-point serial connection to move data at 3. All the different SCSI varieties use controllers and cables to interface with devices. We'll look at this process next. Also called a host adapter , the controller can be a card that you plug into an available slot or it can be built into the motherboard.

This is a small ROM or Flash memory chip that contains the software needed to access and control the devices on the bus. For example, if the bus can support sixteen devices, their IDs, specified through a hardware or software setting, range from zero to The SCSI controller itself must use one of the IDs, typically the highest one, leaving room for 15 other devices on the bus.

Internal devices connect to a SCSI controller with a ribbon cable. External SCSI devices attach to the controller in a daisy chain using a thick, round cable. In a daisy chain, each device connects to the next one in line. For this reason, external SCSI devices typically have two SCSI connectors -- one to connect to the previous device in the chain, and the other to connect to the next device.

Different SCSI variations use different connectors, which are often incompatible with one another. These connectors usually use 50, 68 or 80 pins. Once all of the devices on the bus are installed and have their own IDs, each end of the bus must be closed.

We'll look at how to do this next. If the SCSI bus were left open, electrical signals sent down the bus could reflect back and interfere with communication between devices and the SCSI controller.

The solution is to terminate the bus, closing each end with a resistor circuit. If the bus supports both internal and external devices, then the last device on each series must be terminated. Types of SCSI termination can be grouped into two main categories: passive and active. Passive termination is typically used for SCSI systems that run at the standard clock speed and have a distance of less than 3 feet 1 m from the devices to the controller.

SCSI also employs three distinct types of bus signaling , which also affect termination. Signaling is the way that the electrical impulses are sent across the wires. Both HVD and LVD normally use passive terminators, even though the distance between devices and the controller can be much greater than 3 ft 1 m.