65-0-1: Setting Up Your SCSI Recorder, By Bob Starrett
Many power users swear by SCSI for its speed, reliability, and maturity. Others hate it for its myriad inflexible rules. I won't take sides, except to say that if you follow these rules to the letter when setting up or changing devices on your SCSI bus, generally things are reliable, fast and trouble-free. As I say this, of course, my SCSI recorder is recognized by my SCSI card only every other time that I boot my computer. It All Starts With Termination Setting up a SCSI CD Recorder is pretty straightforward if it's your only SCSI device.
Assuming your SCSI card is installed properly, you just need to make sure that termination is set to "automatic" (or "enabled" on older cards). If your SCSI adapter has a BIOS, you can check termination by pressing Control-A as your computer is booting, which brings you to the SCSI card configuration page. To start, everything else can be left at the default settings. As you get more experienced, or add devices, you may want to tinker with some of the other settings for optimal performance.
Next, make sure your SCSI recorder is also terminated. Every SCSI device, internal or external, has its own method for termination. For internal devices, it is often a jumper; for external devices, a jumper or switch. If you're not sure how to set it, check your recorder's manual. Finally, boot up your PC and look in your drive list to check that Windows can see the recorder. If so, you should be all set to fire up Easy CD Creator. One other important thing to note are that SCSI devices are generally NOT plug-and-play. You should turn your recorder on, and have it connected to your computer, before booting up your system. And do not disconnect it unless you have turned off your computer. Damage to your hardware could result.
If you have multiple SCSI devices, termination gets a little more complicated, one improper setting can bring the entire SCSI chain to a halt, and adding or moving a device often means you'll have to change another device's settings. Fortunately, understanding that both ends of any SCSI chain must be terminated, while intermediate devices must not, will solve most problems. Your SCSI card sits at the end of the chain unless you have both internal and external devices. Then the SCSI card is in the middle of the chain and its termination must be disabled. Catching the Right Bus While termination is the most common cause of SCSI setup problems, there are several other rules to follow that are especially important when you have multiple devices. Generally a SCSI bus, or chain, can handle up to 8 or 15 SCSI devices (including the card itself), depending on whether it is a Narrow or Wide bus. If your SCSI card's model number has a "W," it's wide, and can handle 15 devices. A wide bus connection also uses 68-pin connectors, rather than the 50 pins of narrow connectors. CD-recorders, scanners, magneto-optical drives, tape drives, and internal or external SCSI hard drives can all go on the same bus, if they are all narrow or all wide devices. If you're lucky, you can sometimes mix narrow and wide on the same bus, with narrow at the end of the chain, but it is not recommended.
Whether your bus is wide or narrow, each SCSI device (including the adapter card) must have also have a unique SCSI ID number. These IDs range from 0 through 7 (or 14 for wide busses). The SCSI card itself is usually set to ID 7 (or 14). Hard drives should be set to ID 0 or 1 to ensure that you can boot from them in all configurations. Set other devices, including your CD recorder, to IDs 2, 3, 4, 5 or 6. Just be sure that each device has a different number. Even if you don't have SCSI hard drives, it is best to leave ID 0 and 1 open, unless you really need to use them.
More on Termination.
Just what is all that termination stuff we discussed at the beginning? And why is it necessary? A terminator is basically a resistor that is attached to a SCSI peripheral or a SCSI card. When signals go across the bus, back and forth between devices, they need to be routed properly so they do not go astray and interfere with the workings of any of the devices on the bus. The basic rule is that both ends of the bus must be terminated. If the SCSI card is the last thing on the bus, on either end, it too must be terminated. Terminators take different forms. They may be small connectors that attach to one of the SCSI ports on an external SCSI drive. They may be internal to the device and set by a switch or jumper. Or they may be actual physical resistors that you need to plug and unplug manually, depending on where on the bus your device is placed. Some devices have no provision for termination, in which case you must use a cable with a terminator built into it and the device must reside at the end of the SCSI bus. Going the distance Another thing that is important to remember about SCSI is that total length of all cabling on a bus, both internal and external, is limited. Fast SCSI and Fast&Wide SCSI limit overall cable length to 3 meters. Ultra SCSI is limited to 3 meters if you have one to four SCSI devices and to 1.5 meters, or 4.9 feet, if you have four to eight devices. Of course, a total 4.9 feet of cabling connecting eight different devices is quite ridiculous in desktop configurations and really only practical for racks of hard drives, each connected by 4-inch cables. Ultra2 and Ultra160 SCSI increases cable lengths to a total of 12 meters connecting all devices. The Bottom Line With so many variables to worry about (excessive cable length, improper termination or conflicting SCSI IDs), SCSI problems can be one of the most difficult things to troubleshoot in all of computerdom. Many times, even with an improper setup, everything works fine, and problems only start to occur when you add a new device, or change something that would not otherwise cause a problem. This may lead you to believe the new device is at fault, when in fact, it is not. So, every time you change something on your SCSI bus, double check ALL IDs, termination and cable length.
Advanced User Tips
If you are comfortable with terms like BIOS settings and ASPI drivers, here are some more things you can do to make sure your SCSI bus is optimized. First, set these SCSI BIOS settings for reliable CD recording: *Synchronous Negotiation: Disable (Enable for 10X and faster recorders) *Maximum Sync Transfer Rate: As slow as possible (higher for 10X and faster recorders) *Disconnection: Enable *Plug & Play SCAM support: Disable *BIOS Support for Bootable CD-ROM: Disable *BIOS support for INT13 devices: Disable (unless booting from a SCSI hard drive on this card) *Support removable media as fixed disk: Enable Next, check that your ASPI drivers are up to date (unless you are using Windows 2000, where it's probably best to stick with what works). Finally, don't upgrade the BIOS on either your recorder or your SCSI card unless the later revision specifically fixes a problem that you are having. As with a motherboard BIOS upgrade, if something goes wrong during the process, your motherboard, recorder or SCSI card may become useless.
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