A. It sounds from your question that you've added a second hard drive to your  system which you have placed on the secondary controller. The first problem  that comes to mind is your hard drive's jumper - if your second hard drive is
the only drive on that controller, it should be jumpered as the primary (master) drive, not a secondary (slave) drive. If problems continue, you may be getting  interference from the CD-ROM - try putting the second hard drive as a slave
drive on the primary channel, then put the CD-ROM as the master drive by  itself on the secondary channel.
 
SCSI
Q. I'm just starting to learn about SCSI, but I find all of the terms to be terribly confusing. What's the difference between SCSI-1, and SCSI-2? What do those "Fast", "Wide", and "Ultra" terms mean?

A. I'm not surprised that you're confused. The problem with SCSI comes from the  fact that it is so versatile and diverse - the SCSI system can exist in many different  variations, so I'll try and clear up the clutter. First, SCSI means "Small Computer  System Interface". It began life in 1979 when Shugart Associates (you might  remember them as one of the first PC hard drive makers) released their "Shugart  Associates Systems Interface" (or SASI) standard. The X3T9.2 committee was  formed by ANSI in 1982 to develop the SASI standard which was renamed SCSI.  SCSI drives and interfaces developed under the X3T9.2 SCSI standard were  known as SCSI-1, though the actual SCSI-1 standard (ANSI X3.131-1986) didn't  become official until 1986. SCSI-1 provided a system-level 8-bit bus which could           operate up to 8 devices, and transfer data up to 5MB/s. However, the delay in standardization lead to a lot of configuration and compatibility problems with SCSI-1 setups.

Earlier in 1986 (even before the SCSI-1 standard was ratified), work started on the SCSI-2 standard designed to overcome many of the speed and compatibility  problems encountered with SCSI-1. By 1994, ANSI blessed the SCSI-2 standard  (X3.131-1994). SCSI-2 was designed to be backwardly compatible with SCSI-1,  but SCSI-2 also provided for several variations. "Fast SCSI" (or Fast SCSI-2) doubles the SCSI bus clock and allows 10MB/s data transfers across the 8-bit  SCSI data bus. "Wide SCSI" (or Wide SCSI-2) also doubles the original data               transfer rate to 10MB/s by using a 16-bit data bus instead of the original 8-bit data  bus. To support the larger data bus, Wide SCSI uses a 68-pin cable instead of a 50-pin cable. Wide SCSI can also support up to 16 SCSI devices. Designers then  combined the attributes of fast and wide operation to create "Fast Wide SCSI" (or  "Fast Wide SCSI-2") which supports 20MB/s data transfers across a 16-bit data bus. Whenever you see references to "Fast SCSI" or "Wide SCSI" or "Fast Wide  SCSI", you're dealing with a SCSI-2 implementation.

But SCSI advancement hasn't stopped there. ANSI began development of the  SCSI-3 standard in 1993 (even before SCSI-2 was adopted). SCSI-3 is designed  to be backward compatible with SCSI-2 and SCSI-1 devices. Although SCSI-3 is still not finalized, there are many SCSI devices and controllers that are making use of  the advances offered by SCSI-3. These early SCSI-3 devices are generally known as "Ultra SCSI" (or Ultra SCSI-3, also termed "Fast-20 SCSI"). Ultra SCSI uses a  20MHz SCSI bus clock with an 8-bit data bus to achieve 20MB/s data transfers.                  By using a 16-bit data bus, SCSI-3 offers "Wide Ultra SCSI" (or Wide Ultra  SCSI-3, also termed "Wide Fast-20 SCSI") which handles 40MB/s data transfers.

For the future, the SCSI-3 standard is also proposing "Ultra2 SCSI" (called Ultra2 SCSI-3 and "Fast-40 SCSI") using a 40MHz bus clock to provide 40MB/s data  transfers with an 8-bit data bus. The 16-bit data bus version is known as "Wide  Ultra2 SCSI" (or Wide Ultra2 SCSI-3, called "Wide Fast-40 SCSI") which is  supposed to support 80MB/s data transfers. Whenever you see references to  "Ultra", "Fast-20", "Ultra2", or "Fast-40", you're faced with a SCSI-3 setup. Table 1 compares these SCSI variations.
 
Also keep in mind that SCSI has traditionally been a "parallel" bus - that is, 8 or 16  bits of data are transferred at a time across parallel data lines. SCSI-3 is proposing  three new serial connection schemes. You'll see these noted as Serial Storage Architecture (SSA), Fibre Channel, and IEEE P1394 (a.k.a. "Fire Wire"). These serial schemes will offer faster data transfers than their parallel bus cousins, but are NOT backward compatible with SCSI-2 or SCSI-1.

You can learn a lot more about SCSI from the SCSI FAQ at:         http://www.cis.ohiostate.edu/hypertext/faq/usenet/scsi-faq/top.html.
 
 
Controller card
 Q. I've been told that CD-ROMS connect to the IDE controller cable, and fast hard drives connect to the EIDE controller cable. Well, do the faster 24X CD-ROM  drives still connect to the IDE cable, or do they connect to something else? What about DVD drives--where do they hook up?

A. That's a great question! The 'speed' of a CD-ROM refers to the speed at which data can be taken from the disc. For a 24X CD-ROM, this rate is about 24 times the speed of a floppy drive interface (150KB/s x 24) or about 3.6MB/s. This speed  is not related to the type of interface that the CD-ROM uses. If the CD-ROM uses a standard (ATA) type of interface (also called IDE), then it's a slower interface that  should stand alone, or with other slower devices, on the secondary IDE controller  channel. If the CD-ROM specifically uses an ATA-2 (sometimes called EIDE)                  interface, then it's capable of much faster data transfers, and should be able to coexist with EIDE hard drives on the primary EIDE controller channel. You'll need to glance at the CD-ROM's spec sheet to determine the exact interface. By  comparison, DVD-ROM drives DO use ATA-2 (EIDE) interfaces, and can easily  connect as 'slave' devices to a 'master' EIDE hard drive on the primary EIDE controller channel.
 
 
 

                                                              SOURCE:  Zdnet and Computer Currents