SCSI information needed plz

[Dorza]

K. i need to find out why SCSI can be temperamental, ive spent the last hour or so useing google to search for this info, but its come back with nothing of much importance or anything which i can write about. So as a last resourt i came here. Has or does anyone know of any webistes which may have this info? Ive looked on howstuffworks, pctech-guide, webopedia, and MS knowledge base, but none of these gave me much info. Thanks for any help

[Mr Meltdown]

SCSI what? Hard disks, scanners, what SCSI card you got etc?

SCSI uses ID numbers and each device needs to be on it's own ID number. 0 is usually a boot disk, (but you can set the target ID for boot disks on your SCSI controllers BIOS).

Basically if you want to test bits and make sure they work before adding other kit (sensible) then have one disk on the controller at a time with the end of the chain terminated. Termination is IMPORTANT in SCSI.

The two rules of SCSI are:

Each device must have it's own SCSI ID.
The end of the chain must be terminated.

Have a rummage around www.adaptec.com they used to have guides etc on there years ago.

CHeers,

MM

[Dorza]

What it is, ive been told to go on the net by one of my teachers and find out the answer to this question.

"Why can SCSI be temeramental ?"

Thats the only information we've been given. As i said i have searched google for a long time, but nothing much has come back. I belive im suppost to find out why the inerface termed as SCSI can be temperamental and not an actual bit of hardware that connects to it.

[Mr Meltdown]

SCSI is only temperamental if it is:

1. Not terminated correctly
2. SCSI IDs are clashing
3. Hardware or cables are faulty
4. Hardware installed beyond stated distance limits for SCSIcables

The word "temperamental" is subjective and is best understood in the context it is written so maybe preceeding questions will give you the clue.

I'd download and read thru the 2940UW manual here as it gives trouble shooting which will answer the question:

http://graphics.adaptec.com/pdfs/ins...940v220_ig.pdf

Have fun.

Cheers,

MM

[spikegifted]

Well, for starters, you can give us a definition of what you mean by 'temperamental'... I'm guess that you mean 'there're lots of opportunities to screw up', then you're right; but in fact it is dead easy and with some basic understanding, you won't go far wrong.

First SCSI can handle up to 16 devices per chain (commonly known as a 'channel'), including the controller, which mean that you can attach up to 15 devices to a single channel controller.

With IDE, you can have only 2 devices per channel, which makes it very easy to identify the devices - it can be either 'master' or 'slave'. However, if up to 16 devices, SCSI require something a little more sophisticated, so you have 'SCSI ID'. Each devices in a SCSI channel has an unique ID - the controller is usually 7 and the rest is for you to decide. However, most people use 0 for the boot disk and up from there.

Due to the way the SCSI bus operate, it needs to be 'terminated' for the bus to operate correctly. Some devices have 'auto-terminate' built in which means you don't have to do a thing. But in other cases, you need to manually terminate the bus, which means you've to physically attach a 'terminator' to the end of the SCSI cable. So watch out...

SCSI, like IDE has evolved over the years. There are many standards and most of them are compatible with each other. Make sure you understand what connection you require before getting the devices and cables. Most modern internal SCSI devices have one of three connections - 50pin (usually optical drives), 68pin (usually HDDs) and 80pin (usually HDD with hotswap). Know what you're after before you pay the £££.

That's all. Make sure you do the homework and enjoy your new equipment.

[slugs]

scsi termination power is another one that can catch you out. at least one device in the chain must power termination power.
also mixing narrow (8bit) and (16bit) scsi devices. a narrow scsi device with a scsi id of 0 will conflict with a wide device with an id of 8