I have a cable that won't run at 100 full. What I need to know is what makes the differance in a cable, wiring or quality?

We are talking about Ethernet here? Providing it is Cat5 it will utilise 100Mbs. The deciding factor is what the cable is connected to and how it is configured. Most switches will run at 100Mbs full duplex. If it isn't, check the NIC isn't set at half duplex. Hubs will only ever run at half duplex. Stuart

thx, everthing in the network is 100 full. All rated 100 full. But some cables wont run at full, example. computer A set to 100 full sending data to computer B, acts like a 56k modem. If I set the nic on computer A to 100 half , I get great speeds. Also computer A when set to full acts like a 56k modem on the net. If I change out the cable its all fine at 100 full. So I know its the cable but what about it. I get some good ones and some bad. I crimp them all the same. I test all leads with an ohm meater, and still some cables don't run at full duplex. is it the quality of the metal? leagth? the cable is 50 feet?

cable lenght is fine. You can go up to 100meters or 328feet. Odds are you don't have the pairs correct. Each pair needs to be "balanced". In other words each pair is twisted together. If you take one line from one pair and another line from another pair you have unbalanced the pairs negating the reason for the pair twists [crosstalk/attenuation] Might want to confirm your wiring by going to any one of a dozen sites online for the correct wiring diagrams.

tankyou, I have a great source. http://duxcw.com/digest/Howto/network/cable/cable5.htm but are you telling me wires 4,5,7,8 are the full dupx lines. and maybe thats my problem. If so thx so much I understand now.

If you are hooking into a router or wireless router the nic should be set as auto as that is all the switches understand , most "low end" switches do not allow you to hardcode the settings . So if you try to hardcode your nic at 100/full you will have a speed/duplex mismatch which will cause really slow response and all kinds of line errors . The reason that 100/half works is because a switch can always sense the speed but cannot sense the duplex unless the other end is set as auto.Because the switch cannot sense the duplex when the client is hardcoded it will default itself to 100/half in your case . In the end the solution is make sure the client nic is set as auto . That's why you get really slow speeds because you are trying to hardcode the speed and duplex , set it as auto .

thank you, This is understood. Although in this case Its a matter of what gives with the cable? I can switch out the cable and set to auto. If I do this I get 100/full with no problems. But if I use the cable in question I get 100/full(auto detect) but bad speeds. It is detecting correct but the cable cant keep up. If I hard code it to 100/half every thing is fine. why this cable? what makes a cable not run at full duplex is the question?