Actual Cat5 speeds

M

miazmaticdotcom

Gawd
Joined
May 3, 2003
Messages
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I know it says "Standard Cat5 cable is not recommended for 1000BaseT distances over 25 ft" in the FAQ, but...

My house is wired with a ragtag assortment of Cat5 and Cat5e. How much speed loss can we realistically expect across a Cat5 segment measuring ~110ft? 500-600mbps or less?
 
I use regular cat5 crossover cable at home sometimes between two computers. The cable is about 10 feet long, and I get speeds of 300-400Mbs. The hard drive on one of the computers is one of the main limiting factor.

Isnt the PCI bus limited to abotu 260Mbs? I see a lot of 32 bit PCI 10/100/1000 cards floating around for sale.
 
The FAQ is wrong.

You won't get any speed loss with GigE over Cat 5 because GigE per spec, only requires 4 pairs of Cat 5 minimum.
 
miazmaticdotcom said:
So what is with people peddling Cat5E, then?
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Cause it's generally slightly cheaper, and easier to work with. Cat6 is a thicker cable which makes it somewhat less flexible. Slightly harder to crimp too, I might add. hehe
 
miazmaticdotcom said:
So what is with people peddling Cat5E, then?
Click to expand...

If I remember right, the official spec allows SOME Cat5 to be GigE certed, because they changed the spec around 1995 if I remember correctly. All Cat5E is certed to run Gbit.

bob said:
I use regular cat5 crossover cable at home sometimes between two computers. The cable is about 10 feet long, and I get speeds of 300-400Mbs. The hard drive on one of the computers is one of the main limiting factor.

Isnt the PCI bus limited to abotu 260Mbs? I see a lot of 32 bit PCI 10/100/1000 cards floating around for sale.
Click to expand...

Crossover for GigE isn't needed, it will auto x-over, and since it uses all 4 pairs, if an x-over was needed, it would have to crossover all 4 pairs, instead of just 1-2, 3-6.

The PCI bus is limited to 133MBbs(megaBYTES per second) for 32 bit 33 MHz busses(if I did my math right.) In theory, GigE can transfer ~120MBps in each direction at the same time if there is enough cpu power and bus bandwidth, in the real world in quite a bit less though.
 
Cat5 is rated up to 100 MHz over a 100 meter distance.
Cat5e is rated up to 350 MHz over a 100 meter distance

Anything over 155 Mbps on Cat5 over an extended run will result in higher collisions and reduced performance.

Cat5e is made with more twists and higher quality to reduce crosstalk. Quality Cat5e rated up to 350 MHz will perform at a Gig with no problems. Your other equipment like the switch or computer I/O board will most likely be the bottleneck.

Cat6 is made with thicker gauge core and is rated up to 1000 MHZ over a 100 meter distance. Cat6 cables also require Cat6 connectors with core blocks to actually be "Cat6".
 
100m is the limit, not 300, maybe youre thinking 300ft

anything over that and another signal could be sent over the same line before the first signal reaches its destination making for confused hardware and retrys.
 
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