On 23/12/2006, at 10:21 PM, Tim Law wrote:
I find it's easy to get confused between the Mega Bit per second
and the
Mega Byte per second. I'm likely to be corrected here,
Okleydokley :-)
but there are 6 bits per byte,
I assume you meant 8 as there are actually 8 bits to the byte (which
from your 8Mb/s = 1MB/s calculation below indicates that is what you
meant to type. :-)
Incidentally, there are 4 bits to a nibble and I'm not making that up
either! :-)
so a download speed of 8 mega bites per second, is actually 1 mega
byte per second -
8 mega bits per second = 1 mega byte per second just to be precise,
though in communications you almost always use bits not bytes.
or 1000k in normally used language.
Interestingly enough, 1 megabit per second does actually = 1000
kilobits per second.
Also, 1 kilobit = 1000 bits
and 1 gigabit = 1000 megabits.
You use decimal not binary for these measures of bitrate or
communication speeds (go figure).
In other areas of computing such as data storage on hard disks you
use the binary number system meaning that:
1KB = 1024 bytes
1MB = 1024KB
1GB = 1024MB
Ah don't you love the consistency of it all.
Providers advertise
the mega bit speed so the numbers look super fantastic.
I currently am using iinet DSLAM and my data rate at the modem is
showing
11082 (Kbps.) and using a download manager I can hold over 1000k
per second
at times.
For those interested in how you should write these units:
1 kilobit is written 1Kb
1 kilobyte is written 1KB
1 megabit is written 1Mb
1 megabyte is written 1MB
Notice lowercase b for bit, capital B for byte. Kilo and Mega are
generally supposed to be capital K and capital B respectively.
So:
8Kbps = 1 KBps
8Mbps = 1 MBps
1Kb/s =1Kbps = 1 Kilobit per second
1KB/s =1KBps = 1 Kilobyte per second
Communications speeds such as the speed of dial-up and ADSL modems,
ethernet and wireless networking are usually described in bits.
Data storage such as hard disk or RAM capacity is usually described
in bytes.
However, you do also have the exceptions where data transfer speeds
of storage devices are sometimes described using either bits or bytes
such as the speed of CD-ROMs being described in bits per second (eg
1x CD-ROM = 150Kbps) while hard disk transfer rates are sometimes
described in bytes per second (eg. 20MB/s) just to confuse everyone.
:-(
What I'm trying to find out is just how close to their advertised
speeds (8
Mega bytes per second) people have found with Telstra Cable,
Actually, that should read as 8 mega bits per second (8Mbps) in this
case which also happens to be the maximum speed ADSL 1 is
theoretically capable of achieving. (just being picky again!)
In our case, we are on iinet's ADSL 2+ service with an advertised
maximum of 24 Mbps depending on distance from the exchange. We are
lucky to achieve 1.3Mbps on a good day as we are about 4kms from the
exchange. :-(
-Mart
