Tricky Questions

Sandra Morrison

I'm anxious to take the A+ Core Hardware exam in the next week. I have a few things I would love help figuring out.

The biggest problem is, despite all of my
studying, I can still be tripped up by, what I consider, tricky wording in a question. For example:

1) I know that a narrow SCSI chain can support 8 devices, a host adapter and 7 devices. On a Passport test, Mike asks, "how many devices can be connected to a SCSI chain?" The answer is 7. If the word "device" is used, is it safe to assume that it is excluding the adapter? What is frustrating is the fact that I stare at the question knowing that if I "interpret" it one way I will answer 8, but if I "interpret" it another way I will answer7.

2)If I'm asked "what processor first used protected mode," should I assume that they mean the 286. If they were referring to the 386, they would have specified "enhanced mode?"

I would love a section in a study guide on CompTia's question phraseology.

3) On p.1163 of A-I-O (3rd Ed.), Mike Meyers shows a diagram of a 10 Base T segment. He clearly specifies that 1 PC can go on a segment with a maximum length of 100m. There can then be a max of 1024 PCs per hub. Then on p. 1169, he shows the Token Ring setup. He shows that the max segment length is 100m for STP and 45m for UTP. It states that there can be a max of 260 PCs on each STP ring or 72 PCs on a UTP ring. Then, as in the 10 BaseT network, it says there can be a max of 1024 PCs per MAU. It seems contradictory or I'm missing the big picture. Also, why is the max segment length using UTP only 45m in Token Ring and 100m for 10BaseT?

Sorry about so many questions. I've got the jitters about taking my first exam.
Thanks for your help!

RussS

Hey Sandra

Q1 - see ....
http://www.techexams.net/technotes/scsi.shtml

Q2 - I wouldn't worry - you won't get that kind of question.

Q3 - Cabling ...... This is probably outside A+ too, but with Ethernet (CSMA/CD) there are many limitations caused by collisions - 1024 is the maximum machines per Hub, but I understand no-one makes a hub that size. The 5-4-3 rule generally applies ... 5 Segments, 4 Repeaters, 3 Populated Segments.

For Ethernet 802.3 CSMA/CD
10Base2 - Coax - 185 metres - BNC conector
10Baes5 - Coax - 500 metres - BNC, AUI
10BaseT - UTP - 100 metres - RJ-45
100BaseT - UTP - 100 metres - RJ-45
100BaseTX - UTP - 100 metres - RJ-45
100BaseF - Fibre - 5 kilometres - SC, ST
100BaseFX Fibre - 5 kilometres - SC, ST

Remembering UTP = Unsheilded Twisted pair
STP = Shielded Twisted Pair
With shielding you are able to have slightly longer cable runs. STP is not usually used for Ethernet unless there are issues with EMI


For Token Ring 802.5
UTP - up to 72 nodes within 45 metres from the Mau.
STP - up to 260 nodes within 100 metres from the Mau.
Coax - I am not sure of there

I hope I have not added to the confusion - most of this is really Net+. For A+ I think knowledge of the OSI (in general) and what sort of connectors are for the different cable types.

Sandra Morrison

Russ,
Your reply was very informative, especially about the 5-4-3 rule. I had not seen that information anywhere and I was curious if the networks had a limit on the number of repeaters, etc.

I asked for so much info that I think one question was overlooked. Can you explain why the distance from the hub (or MAU) using UTP cable is 100m for 10BaseT, but only 45m for Token Ring?

Thanks again for your super effort!

RussS

Hey Sandra
Most of that is Net+ stuff so you wouldn't have seen it. I do have to admit that I viewed the Net+ Disk that comes with Mike Meyers All In One book prior to the A+ and I believe that gave me a much better understanding of the networking requirements.

The different in distances are really not that great. I guess the easiest way is to imagine a straight line of 100M - that is the distance a signal will travel on a bus using CSMA/CD... now with Token imagine putting the Mau at the 1/2 way point .. 2 x 45=90 - allow for extra degredation with the extra connectors and you are about equal.