SCSI Question
 

There has to be at least a few computer pros here so I ask this question:

I am building a computer within two weeks. Among other things, I will have three SCSI devices: Hard Drive, Burner, and DVD Drive. My questions are these: What is a terminator? What's the difference between male and female terminators? Do I need to get them or is it included? If I do need to get them, where is the best place to get them?

I plan to buy a Adaptec 19160 SCSI Card. The type of hard drive is going to be either a 18GB or 36GB Seagate Cheetah 15000RPM U160. The burner will be a Plextor 12x10x32 and the DVD drive will be a Pioneer 10x40.

Thanks. :1orglaugh

Well When you connect wires to each other there is one part which has little metal endings sticking out (male) and the other part which has holes for the male parts (femal) this of anatomy

Do I need to get a terminator like this though?

you won't need one. It's to connect to scsi cables with each other to make a long one. Probably not included

Well, the hard drive is going to be 68-pin so I guess that goes by itself but the burner and DVD drive are both 50-pin. All I need is a dual device 50-pin cable like this. BTW, are these cables for ONE 50-pin device or two? The site does not say.

you need this type


http://www.egri.co.uk/images/terminator.jpg

Arg -- I'm stupid.

I would use one 68 pin cable and then get two 50 pin adapters for the older devices.

What OS is this for?

Windows XP Pro.

Here are the cables I plan to buy, tell me if I am doing something wrong:

50-pin Dual Device cable (they don't have single device)

Two of these for the 50-pin devices

So would I need to buy a terminator for any of this? If so, what kind of terminator and where is the best place to buy it?

Why not just use 1 68 element ribbon for all devices and adapt the 50 pin devices? You can get all this for about $10 here.

You wont have to terminate as long as your card has the last SCSI ID. Usually by default it's 9 , and your HD will be 0.

How can I adapt a device? Is it easy?

Yah there are little 68 to 50 pin adapters available. So all you need is one ribbon for the whole setup.

The website you mentioned above almost certainly has these.

Would it be better for me to adapt my 68-pin U160 scsi to 50-pin NON-U160 or adapt the two 50-pins to 68-pin ?

You've got some incorrect answers on this thread. This is the correct answer. A SCSI bus consists of 2 terminators, and a bunch of devices. All SCSI busses must be terminated at both ends to function properly. If you do not terminate, you will find errors in your system logs relating to bad reads, and the net result is slower performance, and occassional data loss.

If you are buying your card in a retail box, it probably includes a cable with a terminator on one end. Usually, SCSI cards have a built in terminator on the card, so it is important that you plug the NON terminated END of the cable into the card, and all the devices must go between the card and the other terminator.

Check with the card manufacturer if the device includes a cable. If it does, it will include a terminator that matches the one on the card. You must not mix active and passive terminators.

Most cards also have an old 50 pin bus somewhere in case you need to hook up older devices. If you plug older devices and newer devices into a new bus, the bus will operate at the SLOWER speed, so don't do this. Most SCSI cards have multiple seperate busses to handle this problem.

SCSI rocks, but so many people that have it think it sucks, because there's so much bad info floating around on how to use it.

Thanks. :)

AdultWire has you on the right track.... and he's right SCSI does rock...... Some fast stuff.... One on my computers has all SCSI

You can put fast SCSI into a 300 Pent. II and it will Rock...

don't know if AdultWire said this but I wouldn't use those cable's you looking at...
get some Ribbon cables..... and if you think you will be adding more drive's get one that has extra ....

okay -- talking with Adultwire right now on ICQ about this :)

adultWire's got it pretty much right on the money.

though usually its 7 thats usually used by
the card, which is a hold over from the days
of 'scsi' what you have now is prolly scsci 3.

scsci used to be centronix connectors, then they went to 'mini' (the 50 pinners) then 68, then all over the place.

50-68 cables are all over the place, but try
for ribbon if these are internal.

termination can be a fun problem, i tend to always terminate, though a vast majority of
consumer level devices will 'auto terminate' for you. usually just by leaving the other cable
off, or by switch. check the manuals well.....

t

OK -- Thanks :)

There really is some talent around here isn't there? Amazing where it pops up.

What somebody said above about many people thinking SCSI sucks is true (them thinking it, not SCSI sucking). Termination is there to prevent signal reflection in the cable. Some of the real high end devices still require active termination to prevent this. The real problem is that many devices work without termination because their interfaces have a high enough resistance themselves, however this throws out the timing fairly often and you get massive degradation in performance and sometimes trouble detecting devices behind these on the chain. Also frequent adapter resets. Add to that the number of people I've seen trying to connect devices in a kind of SCSI 'T Bus' config and it's easy to see why some people think it sucks.

When you get it right there is a night and day difference in performance that nothing else really touches.

Okay -- I have everything straight now with what I am going to get. Thanks guys.

Glad I could be of help, and thanks for the advice as well.. ciao!

a small addition to willow's post....

note, you are dealing with different versions of the scsi spec, 50 pin (usually called scsi 2) vs
68 pin (not sure if this is technically scsi 3, or just transport, disk really isn't my thing(outside of fcal)) the problem/difference is the rated speed of device is different per spec/scsi version.

scsi
fast and wide scsi
ultrwide scsi

etc

an idea would be to have the older spec'd equipment further on down the chain.

host-->68pin-->50pin-->50pin+terminator

Ummm aren't those Adaptec cards self terminating? So if the card is ID9 and your boot is ID0 where do you terminate?

Here's a few more answers for the curious.

1. Yes, the 50 pin stuff is older spec. But a SCSI bus can only operate at one speed at a time. That means, if you put 50 pin stuff and 68 pin stuff together, you get old slow SCSI speeds PERIOD. 20 or 40 MB/s, instead of 160.. to ALL devices. But that card can accommodate 2 chains.. a slow one, and a fast one.. so that's the solution ERU is going to go with.

2. Yes, the card is self terminating, but a SCSI bus (read: a scsi wire) needs to be terminated at BOTH ends. Most drives include terminators that can be enabled with a jumper, but they SUCK compared to a good dedicated termination device. Eru will be using the INCLUDED TERMINATED CABLE with his 68 pin devices, and using the built in terminator on his CD-ROM burner for the 50 pin chain. 50 pin SCSI stuff isn't quite as picky as 68 pin stuff.

The bottom line is.. most shops don't know how to do SCSI correctly.. just like they don't know how to do RAID or AMD correctly. If you want to do it.. do it yourself, and make sure you do your reading. SCSI is not quite childsplay (although it's not terribly difficult) and if done right, will whoop major ass.

Oh, shoplifter.. just for clarity, Termination and SCSI ID's have absolutely nothing to do with each other. Although the terminator is physically located on the SCSI card, it is not part of the mechanics of the SCSI card. A terminator is just a little block of resistors. Usually there are some on the card, and some on the other end of the wire. If you hook up your SCSI card in the middle of your SCSI wire, and you use the on board terminator, welcome to error city.

AdultWire knows what he's talking about. I use SCSI drives myself and they rock.

On our boxes we usually have 3 physical devices 0, 1, and 9 (two HD's and the card) on a 3 plug ribbon....We have never used a terminator or a terminating cable. I use IDE devices for CD and Tape.

Is there any potential performance hit to this?

I am actually very curious about the performance of Eru's SCSI DVD drive VS IDE. Is DVD playback smoother in any way with this drive? If so I may run out and get one. I was thinking of picking up an ata133 IDE DVD whenever they are available here previously.