gmusgrave
Aug 14, 2011, 9:20 AM
Post #10 of 16
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Re: [YucaLandia] magicjack service in MX
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This is a bit OT for the MagicJack topic, but I'd like to try and clear up some of the confusion about units used for download/upload speed, if I can.
Some speed test websites use "K" in their reporting, some official units-conversion websites use "K", but the typical accepted convention seems to be "kbps" where "kbps" formally means kilo bits per second while "Kbps" = kilo bytes per second.
The SI (metric) standard for prefixes is: kilo (1,000) = "k", mega (1,000,000) = "M", giga (1,000,000,000) = "G", and tera (1,000,000,000,000) = "T". All of these are commonly used in computer and telecom to specify data size and speed.
The correct unit for kilobits is "kb" and for megabits is "Mb".
There is also an accepted computer science designation for the symbols used for bits and bytes: bits have a unit designation of "b" and bytes are designated with "B". Kilobits are "kb" and kilobytes are "kB". This is a very important distinction, since otherwise you can't tell them apart, and there is a significant difference: 1 byte = 8 bits.
Therefore, "kbps" is kilobits per second, while "kBps" is kilobytes per second. "Kbps" has no accepted meaning.
For example, a 1 Mbps (megabits per second) connection means that the maximum achievable download bandwidth is 1 million bits per second, which is 0.125 MBps (megabytes per second). A 0.5 MBps connection is the same as a 2 Mbps connection – bad marketing, since 2 Mbps sounds faster than 0.5MBps.
If this confuses you, cross-check the file sizes in bits, bytes, Mb and Gb in your file manager (each give different results), and then check out the actual size in bits or bytes of your 180G hard drive etc.
I think this should read, "...the file sizes in bits, bytes, MB and GB...". Most modern file managers normally report file size and free disk space in bytes, and so these are megabytes and gigabytes respectively.
Unfortunately, there are problems with the quantities these units might represent when reported by an operating system (see the end of my next comment).
There are no single conversion or reporting rules when comparing base-10 decimal-thinking units and base 2 computer units: 1,000 Kilos does not necessarily equal a Mega, and 1,000 Megas do not necessarily equal a Giga.
Unfortunately there really is some confusion here. The quantity referred to by the units kilobyte (kB), megabyte (MB), and gigabyte (GB) depends on their context!
They should have the SI metric meaning where: 1 MB = 1,000 kB and 1 GB = 1,000 MB. Unfortunately, there are a couple of exceptions.
When used for media capacity (such as a hard drive), a MB, for example, does mean "one-million bytes". The same usage applies to telecom data (such as download/upload speeds): 1 Mbps = 1,000 kbps. This is the metric SI standard adopted by the IEEE and the IEC.
Unfortunately, confusion results because computer memory capacity (RAM) uses a binary rather than a metric meaning for these units. This is because memory is a hardware-level device that can only be addressed in base-2. In this context, 1GB, for example, is 1,073,741,824 bytes (rather than the expected 1,000,000,000). In this system, 1 kB = 1,024 bytes, 1 MB = 1,024 kB, and 1 GB = 1,024 MB.
There have been units introduced to solve this problem. They are called "kibibyte", "mebibyte", "gibibyte", and "tebibyte". The "bibyte" suffix stands for "binary byte".
These new terms represent a binary factor of 1,024, rather than the metric standard of 1,000. There are also corresponding terms for bits ("kibibit" for example). A kibibit per second would be written as "Kib/s", and a kibibyte per second would be written as "KiB/s".
The intention was that the SI units be only used for powers of 10, and never for powers of 2 – this latter is where the new units come in. Unfortunately, these new units have been virtually ignored by the memory industry.
Consumers would naturally assume that 4GB of RAM, for example, would be same as 4GB of hard drive space. Sadly, because of the difference between the non-standard usage of these units when talking about memory capacity, this is not the case. 4 GB of RAM is 4,294,967,296 bytes, where 4 GB of hard drive space represents 4,000,000,000 bytes (as you'd expect). Hard drive manufacturers clarify this in their drive specs, and usually on the label on the drive. This is because they appear to be the bad guys in this scenario. It looks to the consumer like they are short changing them on capacity. This is not the case.
The problem is simply the non-standard usage of these units by the RAM manufacturers. The hard drive guys are actually in step with everybody else....well almost everybody.
To add even further to the confusion, Microsoft Windows reports file size and free disk space using a factor of 1,024, while Mac OS and Linux use the standard 1,000. Therefore, the file size reported by a file manager for the same data varies depending on the operating system!
In Windows, there will also be a disagreement between the reported file size and the actual capacity of the hard drive because Windows is using a non-standard meaning for MB, GB, and TB which differs from the standard being used by the drive manufacturer.
I hope this clears up some of the confusion surrounding this complicated topic, and helps people better understand the units involved.
Garry Musgrave
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