Your computer has a Dual Channel Ultra2 LVD SCSI card. This peripheral component interconnect (PCI) card allows you to connect devices that use the Small Computer System Interface (SCSI). SCSI is a standard method for connecting disk and cartridge drives, CD-ROM drives, scanners, and other devices. A SCSI port permits high-speed communication between the computer and the device.
You can connect internal and external SCSI devices to the card using SCSI cables. You can purchase SCSI cables from an Apple-authorized dealer or retailer.
Advantages of Your Dual Channel Ultra2 LVD SCSI card
Your Wide Ultra2 Dual Channel SCSI Card has two data channels and uses Low Voltage Differential (LVD) technology.
This technology provides the following benefits:
- High data transfer rates: Your card can transfer information over a single channel at up to 80 megabytes (MB) per second, twice as fast as Ultra SCSI devices. When the card's two channels are in use at once, the card can transfer information at up to 160 MB per second.
- Connect more devices: You can connect up to a total of 30 SCSI devices to the card (15 per channel) internally and externally (limited by the number of internal devices your computer is designed to hold).
- Use of longer cable lengths: The cables used to connect a chain of Ultra2 SCSI devices can be up to 12 meters (about 39 feet) long facilitating easy positioning of external devices.
- Compatible with older SCSI devices: You can connect other SCSI devices that are not as fast as the Ultra2 SCSI, such as Ultra Wide, Ultra Narrow, Fast, and Standard SCSI devices.
Note: Older SCSI devices must use SCSI Manager 4.3 compliant drivers. To determine if your device works with SCSI Manager 4.3, see your SCSI device documentation.
You can connect two chains of SCSI devices to your card, one chain to each channel. You can arrange devices so that Ultra2 SCSI devices can perform at their optimum transfer rate on one channel, while older devices that perform at slower rates can be assigned to a second channel.
Important: If you mix different kinds of SCSI devices that run at different speeds on one channel (internal or external), the channel will operate in single-ended mode for older SCSI devices with a top transfer rate of 40 MB per second.
Note: Make sure you use a SCSI cable compatible for use with Ultra2 devices that have Low Voltage Differential (LVD) technology.
About Connecting SCSI Storage Devices
You can connect SCSI devices in a chain. The first device connects to one of the SCSI card's connectors, the next device connects via a cable to the first SCSI device, and so on. The card has an external cable connector for external SCSI devices and three internal connectors for internal devices.
Channel A serves the external cable connector and one 68-pin internal connector. Channel B serves the other 68-pin internal connector and a 50-pin connector for connecting older internal SCSI devices (although it is not recommended that you install older narrow SCSI devices internally).
All devices connected to channel A connectors are part of a single SCSI chain. Likewise, all devices connected to channel B connectors are part of another SCSI chain. You can connect up to 15 total devices to each channel for a total of 30 devices (although your computer may not be able to house this many devices internally.) The Apple Power Macintosh G3 (Blue and White) is designed to house three internal SCSI devices.
About Channel Data Transfer Rates
The SCSI transfers information in one of two modes: Ultra2-LVD mode or single-ended mode.
In Ultra2-LVD mode, a chain of Ultra2 SCSI devices can transfer data at their fastest speed, 80 MB per second. However, if you connect a slower SCSI device to the chain, the channel defaults to a slower single-ended data transfer mode.
In single-ended mode, a channel can support different data transfer rates from each device up to a top rate of 40MB per second. For example, if you connect mixed SCSI devices that have different transfer rates, each device transfers data at its own speed without affecting the transfer rate of other devices on the channel. An Ultra SCSI device can transfer data at 40MB per second, the top speed for the channel, and another slower device transfer data at a slower rate. In single-ended mode, however, Ultra2 SCSI devices can only transfer data at 40 MB per second, half their potential rate.
When you plan your chain of SCSI devices, take into account whether you want the chain to operate in Ultra2-LVD mode or single-ended mode.
Make Sure Each Device In a Chain Has a Unique ID Number
Each SCSI device in a chain connected to your card must have its own unique ID number from 0 to 15 per channel. (The number 7 is assigned to the card.) You can assign ID's from 0-6 and 8-15. The SCSI ID number helps the computer keep track of the devices when several devices in the SCSI chain are communicating with the computer simultaneously.
The SCSI devices can be in any physical order in the chain; it is not necessary to arrange them in numerical order. See the instructions that came with each SCSI device for information on checking and setting its SCSI ID number.
Important: If two or more devices in a chain have the same ID number, your computer may not start up properly, your equipment may malfunction, and you may lose data as a result.
Use the Right Type and Length of Cable
Your computer includes a cable for connecting up to three internal SCSI devices.
To attach an external SCSI device to your computer or to another external device, always use SCSI cables that are double-shielded, such as Apple SCSI cables. Never use printer-type RS-232 cables. Poor-quality SCSI cables are often the cause of SCSI problems. Avoid mixing brands and types of SCSI cables.
Keep the cables between SCSI devices as short as possible.
Important: The maximum cable length that you can use depends on the types of devices in the chain. See the information below about maximum cable lengths:
| SCSI device | Maximum cable length |
| Wide Ultra2 | 12 meters (about 39 feet) |
| Ultra | 1.5 meters (about 5 feet) |
| SCSI-1, SCSI-2 | 3 meters (about 10 feet) |
Note: The internal cable connected to the card represents one meter of cable length. For example, when you connect Ultra external devices, the internal cable takes up one meter of the 1.5 meter maximum length, leaving .5 meters of cable length for connecting devices.
Terminate the SCSI Chain Properly
To ensure accurate transmission of information, a terminator must be present at each end of a SCSI chain. When you connect SCSI devices, make sure that only the last external device in the chain has a terminator. (The second terminator at the beginning of the SCSI chain is inside your computer.)
The cable supplied for internal SCSI devices within your computer is already correctly terminated.
To terminate the last device in an external chain, do one of the following:
- Use a device that has a built-in terminator as the last device in the chain.
If you wish to attach two or more SCSI devices that have built-in terminators, an Apple-authorized service provider can remove the extra built-in terminators.
- If the device at the end of the SCSI chain does not have a built-in terminator, attach an external terminator. You can attach or remove external terminators yourself. Terminators are available at authorized Apple dealers.
Important: Do not attach a terminator to a device that already has a built-in terminator. If you do, your computer may not start up properly.
Connecting an Internal SCSI Storage Device
To install an internal SCSI device, see the setup manual that came with your computer. It's recommended that you connect internal SCSI devices to channel B.
Connecting an External SCSI Device
To connect an external SCSI device to your card, follow the instructions below. Use these general instructions in conjunction with the more specific instructions that came with your external SCSI device.
1. Shut down your computer and make sure the SCSI device is switched off.
2. Use a SCSI cable to connect the device either to the card's external SCSI connector or to the last SCSI device already in the chain.
Use a SCSI cable that is compatible with the SCSI device. For more information, see the documentation that came with the SCSI device.
Use the thumbscrews on the connectors to make a tight, reliable connection. Do not overtighten the thumbscrews.
3. Turn on all devices in your SCSI chain.
Important: Always turn on all external SCSI devices connected to your computer before turning on the computer itself. Otherwise, your computer won't recognize that the SCSI devices are connected to it and your computer may not be able to start up.
4. Turn on your computer.
Icons appear for all SCSI devices connected.
Note: If you do not see an icon for a device, you may need to use drive formatting software, such as Drive Setup, to mount the device and make it available for use.
5. Install any necessary device drivers (software that makes a device work with your computer).
Drivers needed for a SCSI device usually come on a disk or CD with the device. (If no drivers come with the device, contact the deviceís manufacturer.) Some older SCSI devices may require updated drivers to work with your computer.
Note: If you experience problems after connecting a SCSI device, see the troubleshooting documentation that came with your computer for possible solutions.
Technical Specifications
- Supports 8-bit and 16-bit Ultra2, Ultra Wide, Ultra Narrow, Fast, and Standard SCSI devices
- Supports up to a total of 30 SCSI devices internally and externally (15 per channel, limited by the number of internal devices your computer is designed to house)
- Transfers data at up to 80 Megabytes per second (MB/sec) on each channel
- Supports SCSI Manager 4.3 compliant drivers only