September 24, 2021

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Why is the transfer rate/speed only 10MB in 10/100 Mbps LAN?

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My motherboard specification say that my LAN speed is 10/100 Mbps, but the MAX data rate, or speed my LAN reaches is around 10MB, why is that? Why do we use 10/100 prefix anyway? What does it actually mean?


Letter “B” in abbreviation “MB” means BYTE. Upper and lower case of letter, B and b, denotes different things:

B = Byte

b = bit

8 bits = 1 Byte

100 Mbps = How many MBps?

100 divided by 8 = 12.5 Mega Bytes per second

So 100Mbps LAN can support up to 12.5MB/s data transfer speed.

Similarly, 1000Mbps = 125MBps and 10Mbps = 1.25MBps

Often, we see the following prefix used in LAN speed specs: 10/100 or 100/1000. The first prefix means that the LAN is capable of operating in 1.25MBps and 12.5MBps modes; similarly, the other prefix indicates that the LAN can operate in 12.5 and 125MBps modes.

The use of Mbps instead of MBps is a marketing gimmick that both internet-service-providers and LAN hardware manufacturers use. Bigger is Better, these companies are using this analogy to attract more customers. Instead of selling a 10MB/s internet connection, companies sell 100Mbps connection; it has a label showing a bigger hence attractive figure, which is 10X greater then 10MB/s.

I personally find this marketing technique quiet misleading, or perhaps I should call it deceiving? So many people are confused about what their actual DSL broadband or LAN speed is. I personally wasted a lot of time trying to increase my LAN speed from 10 to 100MB/s when in fact my LAN could only support a MAX speed of 12.5MB/s. I wasted a lot of time before I realized that 100Mb/s means Mega bit, not Mega Byte.

When I first searched the internet, I found few solutions to resolve my LAN speed problem. I bought an expensive LAN cable in hopes that this will finally let me have a full 100MB data rate between my PCs. Obviously, it made no difference what so ever and I kept searching for more answers. I tried changing every settings in my LAN driver, but to no avail. All my attempts to achieve full speed in LAN failed. Finally, I found the correct answer on the internet. My LAN could never deliver 100MB speed; its max data rate is 100Mb, so 12.5MB is the max speed I can get.

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