Setting the SCSI I.D.

ricktea

I read that there might be some Questions on
setting the actual SCSI i.d. and figuring out
what the value of each jumper is. Can someone
explain please what the value is of each of the
3 jumpers and what is the simple equation of
how to figure out how to set 0-7 or 8-15
I.D.'s I just can't figure it out. Thanks, Ric

TheShadow

If you only have three jumpers then it must be narrow SCSI. The jumpers have the binary bit values of 4, 2 and 1; so for example an ID of 5 would be on off on and the highest ID allowed is 7. Wide SCSI needs 4 jumpers with the binary bit values of 8,4,2,and 1 so an ID of 9 would be on off off on. You have learned binary already right?

ricktea

hi, I have never learned binary, but are you saying on regular SCSI
the jumpers have the definate numbers going from left to right of:

4 2 1 ?

so to set an ID of 5, I would leave the first jumper on which is 4,
and then turn the second jumper off, but leave the last jumper which is 1, which total 5. is this correct. Does the order of 4, 2, 1 always stay the say on the jumper going from left to right ? So if I wanted an ID of 1 ...... I would starting from the left side turn the 4 and the 2, off and just leave the 1. Is this correct. Thankyou again Ric

kujayhawk93

You NEED TO LEARN BINARY if you expect to work in the IT field, end of story.

TheShadow

You absolutely must learn binary and its shorthand hexadecimal or you will not survive even a job interview technical exam. It is the kindergarden math of the IT world. Computers only count in binary, on off, true false, 1 and 0. Everything else is done by conversion. Look and the three columns below.

decimal binary hex
0 0000 0x0
1 0001 0x1
2 0010 0x2
3 0011 0x3
4 0100 0x4
5 0101 0x5
6 0110 0x6
7 0111 0x7
8 1000 0x8
9 1001 0x9
10 1010 0xA
11 1011 0xB
12 1100 0xC
13 1101 0xD
14 1110 0xE
15 1111 0xF
16 10000 0x10

That should get you started, in rare instances you may also need to learn Octal. Here is a tip, open up the windows calculator, go to view and set it to scientific mode. You will then be able to do direct conversions between decimal, octal, hexadecimal and binary. Since the calculator is on every windows system you can practice anywhere that you have computer access.

Plantwiz

kujayhawk93 wrote:

You NEED TO LEARN BINARY if you expect to work in the IT field, end of story.

Agreed!


TheShadow provided you with a nice quick refernce, but you need to learn how to figure out 1, 2, 3, 4, 5, etc... on your own for field work anyway. So memorizing is good, understanding is best.

Go through the Binary Math tutorials here:
http://www.learntosubnet.com/

ricktea

thankyou all for the great guidance and examples
you have given me. I will pratice these, I was hoping
this would not be on the test, but I'm glad I found out now.

thanks again, ric

Plantwiz

ricktea wrote:

...... I was hoping
this would not be on the test, but I'm glad I found out now.

thanks again, ric

Rick have you downloaded the objectives to review the material that the exams will cover? If it is on the objectives, it's in the cadidates best interest to KNOW it.

The A+ exams have the lowest passing score, but to enter any exam with the hope that there won't be many (or any) questions on a topic is really a poor habit to develop so early in your exam career. FWIW

DirtySouth

Rick,
I'm going to have to respectfully disagree with most of the others. Knowing binary is NOT mandatory to "make it" in the IT field. That's BS. However, it is covered slightly on the exam & you will benefit from understanding it. It sounds like you already have the basics down.

In order to calculate the binary equivalent of any number you have to understand that each digit in binary (right to left) doubles. Each digit is simply a place-holder. For example:

128 - 64 - 32 - 16 - 8 - 4 - 2 - 1

So, 11111111 = 255 (128+64+32+16+8+4+2+1).

A good trick to remember is that even numbers will always have a list digit of 0 and odd numbers will always have a last digit of 1. There are tons of websites that will explain this far better than I can, so do some searching when you get a chance. Good Luck!

TheShadow

Strange response. If you did not know binary how would you get through subnetting on that CCNA that you are pursuing. If you had not learned it you would not be able to write the post that you did. How would you handle the output from a Blue Screen of Death without knowing binary and Hex or use debug to patch a program. The examples go on and on.

I am not sure what your definition of IT is but I have used binary and hex almost every day for the last several decades. Maybe the knowledge that techs need is getting dumbed down but I seriously doubt it.

kujayhawk93

DirtySouth wrote:

In order to calculate the binary equivalent of any number you have to understand that each digit in binary (right to left) doubles.

While this statement is not incorrect, it's not the most accurate explanation of how the binary system works either. Each digit, right to left, represents a power of 2. The far right digit represents 2^0 (1), then 2^1 (2), 2^2 (4), and so on and so on. Knowing this, you could look at the binary number 10000 and know just by counting the digits that the decimal equivalent is 2^4=32, instead of having to go 2, 4, 8, 16, 32.

ricktea

thankyou, it was a little confusing. If am correct , then
if they ask on a question to set a scsi id to :

7 = 111
6 = 110
5 = 101

Thankyou all very much, I'm just practicing this and I appreciate
your lengthy replies and explaination, it is all invaluable to me.,
and I have printed all this information up.

P.S. What if there are more than 3 pins on the SCSI Aaptor

DirtySouth

TheShadow wrote:

Strange response. If you did not know binary how would you get through subnetting on that CCNA that you are pursuing.

Were not talking about CCNA here...were talking about A+ If this guy was studying for CCNA, I would DEFINITELY encourage him to know binary like the back of his hand.

All I'm saying is that you don't have to know binary to be a good "IT Person". I realize "IT Person" could mean a million different things, but in regards to desktop support I don't think its really a MUST, however it is good to know. I just don't like to hear people bagging on Rick because he doesn't understand binary. People should try to be a little more encouraging.

DirtySouth

kujayhawk93 wrote:

While this statement is not incorrect, it's not the most accurate explanation of how the binary system works either. Each digit, right to left, represents a power of 2. The far right digit represents 2^0 (1), then 2^1 (2), 2^2 (4), and so on and so on. Knowing this, you could look at the binary number 10000 and know just by counting the digits that the decimal equivalent is 2^4=32, instead of having to go 2, 4, 8, 16, 32.

Thanks...I wasn't trying to write a dissertation on binary, just giving him a quick & dirty (no pun intended ) rundown.

Like I said before:

DirtySouth wrote:

There are tons of websites that will explain this far better than I can, so do some searching when you get a chance.