A question of maths

Discussion in 'NZ Computing' started by Philip, Apr 15, 2006.

  1. Philip

    Philip Guest

    How do I work out how long it would take do download a certain amout of
    data at a given nominal speed?

    Say I have a 100 MB file to download and I am connected at 256 kBit/s.
    What's the easy equation? And how do I scale this to work out times at
    different speeds.

    I know the real speeds achieved differ from what's advertised, but I
    want first to consider the theoretical perfect transfer.

    Philip
     
    Philip, Apr 15, 2006
    #1
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  2. Philip

    MarkH Guest

    Philip <> wrote in news:44402a79$:

    > How do I work out how long it would take do download a certain amout of
    > data at a given nominal speed?
    >
    > Say I have a 100 MB file to download and I am connected at 256 kBit/s.
    > What's the easy equation? And how do I scale this to work out times at
    > different speeds.


    256Kbit/s divided by 8
    = 32 KB/s x 60
    = 1920KB/minute x 60 / 1024
    = 112.5 MB/hour

    In practical terms if you get pretty good speeds 30KB/s or better than you
    could expect to download 100MB in about an hour or so. If you get 105 -
    110 MB per hour then you are getting close to the theoretical maximum
    speed.



    --
    Mark Heyes (New Zealand)
    See my pics at www.gigatech.co.nz (last updated 5-September-05)
    "The person on the other side was a young woman. Very obviously a
    young woman. There was no possible way she could have been mistaken
    for a young man in any language, especially Braille."
    Maskerade
     
    MarkH, Apr 15, 2006
    #2
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  3. Philip

    Jerry Guest

    MarkH wrote:
    > Philip <> wrote in news:44402a79$:
    >
    >
    >>How do I work out how long it would take do download a certain amout of
    >>data at a given nominal speed?
    >>
    >>Say I have a 100 MB file to download and I am connected at 256 kBit/s.
    >>What's the easy equation? And how do I scale this to work out times at
    >>different speeds.

    >
    >
    > 256Kbit/s divided by 8
    > = 32 KB/s x 60
    > = 1920KB/minute x 60 / 1024
    > = 112.5 MB/hour
    >
    > In practical terms if you get pretty good speeds 30KB/s or better than you
    > could expect to download 100MB in about an hour or so. If you get 105 -
    > 110 MB per hour then you are getting close to the theoretical maximum
    > speed.


    why the 1024? A megabyte is 1 million bytes; 1000 x 1000; 1,000,000 bytes.
     
    Jerry, Apr 15, 2006
    #3

  4. >
    > why the 1024? A megabyte is 1 million bytes; 1000 x 1000; 1,000,000
    > bytes.
    >


    Have Western Digital paid you to say that? :p

    Steve
     
    Stephen Williams, Apr 15, 2006
    #4
  5. Philip

    Murray Symon Guest

    On Sat, 15 Apr 2006 13:44:38 +1200, Jerry wrote:

    > MarkH wrote:
    >> Philip <> wrote in
    >> news:44402a79$:
    >>
    >>
    >>>How do I work out how long it would take do download a certain amout of
    >>>data at a given nominal speed?
    >>>
    >>>Say I have a 100 MB file to download and I am connected at 256 kBit/s.
    >>>What's the easy equation? And how do I scale this to work out times at
    >>>different speeds.

    >>
    >>
    >> 256Kbit/s divided by 8
    >> = 32 KB/s x 60
    >> = 1920KB/minute x 60 / 1024
    >> = 112.5 MB/hour
    >>
    >> In practical terms if you get pretty good speeds 30KB/s or better than
    >> you could expect to download 100MB in about an hour or so. If you get
    >> 105 - 110 MB per hour then you are getting close to the theoretical
    >> maximum speed.

    >
    > why the 1024? A megabyte is 1 million bytes; 1000 x 1000; 1,000,000
    > bytes.


    cue flame war ... (but yes, you're right Jerry).

    In reality you can use either figure as it is only an estimation and
    your Internet speed is likely to be the most variable factor, anyway.
     
    Murray Symon, Apr 15, 2006
    #5
  6. Philip

    MarkH Guest

    Jerry <> wrote in news:44404d66$:

    > MarkH wrote:
    >> Philip <> wrote in
    >> news:44402a79$:
    >>
    >>
    >>>How do I work out how long it would take do download a certain amout
    >>>of data at a given nominal speed?
    >>>
    >>>Say I have a 100 MB file to download and I am connected at 256
    >>>kBit/s. What's the easy equation? And how do I scale this to work out
    >>>times at different speeds.

    >>
    >>
    >> 256Kbit/s divided by 8
    >> = 32 KB/s x 60
    >> = 1920KB/minute x 60 / 1024
    >> = 112.5 MB/hour
    >>
    >> In practical terms if you get pretty good speeds 30KB/s or better
    >> than you could expect to download 100MB in about an hour or so. If
    >> you get 105 - 110 MB per hour then you are getting close to the
    >> theoretical maximum speed.

    >
    > why the 1024? A megabyte is 1 million bytes; 1000 x 1000; 1,000,000
    > bytes.


    Is that a special size for pedants, or are you talking about common usage?

    Try this:
    Right click a large file and select properties, check size.
    In Windows: 349MB (366,231,552 bytes)
    In Linux: 349.3MB (366,231,552 bytes)

    In common usage 1MB=1024x1024


    --
    Mark Heyes (New Zealand)
    See my pics at www.gigatech.co.nz (last updated 5-September-05)
    "The person on the other side was a young woman. Very obviously a
    young woman. There was no possible way she could have been mistaken
    for a young man in any language, especially Braille."
    Maskerade
     
    MarkH, Apr 15, 2006
    #6
  7. Philip

    -=rjh=- Guest

    Philip wrote:
    > How do I work out how long it would take do download a certain amout of
    > data at a given nominal speed?
    >
    > Say I have a 100 MB file to download and I am connected at 256 kBit/s.
    > What's the easy equation? And how do I scale this to work out times at
    > different speeds.
    >
    > I know the real speeds achieved differ from what's advertised, but I
    > want first to consider the theoretical perfect transfer.


    It's been done a thousand times before, writing a javascript calculator
    is trivial, so there are heaps of these on the web.

    http://www.t1shopper.com/tools/calculate/downloadcalculator.shtml


    http://www.intel.com/personal/resources/broadband/calculator.htm
     
    -=rjh=-, Apr 15, 2006
    #7
  8. Philip

    Enkidu Guest

    Philip wrote:
    > How do I work out how long it would take do download a certain amout of
    > data at a given nominal speed?
    >
    > Say I have a 100 MB file to download and I am connected at 256 kBit/s.
    > What's the easy equation? And how do I scale this to work out times at
    > different speeds.
    >
    > I know the real speeds achieved differ from what's advertised, but I
    > want first to consider the theoretical perfect transfer.
    >

    256kbps is 256 x 1024 bits per sec = 262144 bps = 32768 Bytes per second.

    100Mb = 104,857,600 Bytes

    Therefore 100Mb at 32768 bytes per second = 104857600 / 32768

    = 3200 second = 53 minutes and 20 seconds.

    I've used a scaling factor of 1024 = 1k. In some circumstances 1k may be
    1000 units.

    To look at it another way, 256kbps = 32kB/sec and you want to transfer
    100MB or 102,400kB. That gives a transfer time of 3200 seconds. Amazing!
    It gets the same answer!

    Cheers,

    Cliff
     
    Enkidu, Apr 15, 2006
    #8
  9. On Sat, 15 Apr 2006 02:24:19 GMT, MarkH <> wrote:

    >Jerry <> wrote in news:44404d66$:
    >
    >> MarkH wrote:
    >>> Philip <> wrote in
    >>> news:44402a79$:
    >>>
    >>>
    >>>>How do I work out how long it would take do download a certain amout
    >>>>of data at a given nominal speed?
    >>>>
    >>>>Say I have a 100 MB file to download and I am connected at 256
    >>>>kBit/s. What's the easy equation? And how do I scale this to work out
    >>>>times at different speeds.
    >>>
    >>>
    >>> 256Kbit/s divided by 8
    >>> = 32 KB/s x 60
    >>> = 1920KB/minute x 60 / 1024
    >>> = 112.5 MB/hour
    >>>
    >>> In practical terms if you get pretty good speeds 30KB/s or better
    >>> than you could expect to download 100MB in about an hour or so. If
    >>> you get 105 - 110 MB per hour then you are getting close to the
    >>> theoretical maximum speed.

    >>
    >> why the 1024? A megabyte is 1 million bytes; 1000 x 1000; 1,000,000
    >> bytes.

    >
    >Is that a special size for pedants, or are you talking about common usage?
    >
    >Try this:
    >Right click a large file and select properties, check size.
    >In Windows: 349MB (366,231,552 bytes)
    >In Linux: 349.3MB (366,231,552 bytes)
    >
    >In common usage 1MB=1024x1024


    Actually, that is now wrong. There is a proper standard for binary
    prefixes that work alongside SI prefixes. Everybody should now be
    doing it right, so there will be no confusion:

    SI Prefixes (decimal):
    http://physics.nist.gov/cuu/Units/prefixes.html

    IEC binary prefixes:
    http://physics.nist.gov/cuu/Units/binary.html

    so 1 MB is 1,000,000 bytes and 1 MiB is 1,048,576 bytes.
     
    Stephen Worthington, Apr 15, 2006
    #9
  10. Philip

    MarkH Guest

    Stephen Worthington <34.nz56.remove_numbers> wrote in
    news::

    > On Sat, 15 Apr 2006 02:24:19 GMT, MarkH <> wrote:
    >
    >>In common usage 1MB=1024x1024

    >
    > Actually, that is now wrong. There is a proper standard for binary
    > prefixes that work alongside SI prefixes. Everybody should now be
    > doing it right, so there will be no confusion:
    >
    > SI Prefixes (decimal):
    > http://physics.nist.gov/cuu/Units/prefixes.html
    >
    > IEC binary prefixes:
    > http://physics.nist.gov/cuu/Units/binary.html
    >
    > so 1 MB is 1,000,000 bytes and 1 MiB is 1,048,576 bytes.


    Actually you are wrong. In common usage 1MB IS 1,048,576!

    In technically correct usage MiB would be used, but I have seen no evidence
    that the common usage has moved to the technically correct prefix.



    --
    Mark Heyes (New Zealand)
    See my pics at www.gigatech.co.nz (last updated 5-September-05)
    "The person on the other side was a young woman. Very obviously a
    young woman. There was no possible way she could have been mistaken
    for a young man in any language, especially Braille."
    Maskerade
     
    MarkH, Apr 15, 2006
    #10
  11. Philip

    Jerry Guest

    MarkH wrote:
    > Stephen Worthington <34.nz56.remove_numbers> wrote in
    > news::
    >
    >
    >>On Sat, 15 Apr 2006 02:24:19 GMT, MarkH <> wrote:
    >>
    >>
    >>>In common usage 1MB=1024x1024

    >>
    >>Actually, that is now wrong. There is a proper standard for binary
    >>prefixes that work alongside SI prefixes. Everybody should now be
    >>doing it right, so there will be no confusion:
    >>
    >> SI Prefixes (decimal):
    >> http://physics.nist.gov/cuu/Units/prefixes.html
    >>
    >> IEC binary prefixes:
    >> http://physics.nist.gov/cuu/Units/binary.html
    >>
    >>so 1 MB is 1,000,000 bytes and 1 MiB is 1,048,576 bytes.

    >
    >
    > Actually you are wrong. In common usage 1MB IS 1,048,576!
    >
    > In technically correct usage MiB would be used, but I have seen no evidence
    > that the common usage has moved to the technically correct prefix.


    From my observation 1,000,000 = 1 Meg is more common than the
    1,048,576. Do youu have proof otherwise?
     
    Jerry, Apr 16, 2006
    #11
  12. Philip

    Guest

    Jerry wrote:
    > From my observation 1,000,000 = 1 Meg is more common than the
    > 1,048,576. Do youu have proof otherwise?


    I think it would be hard for him to prove anything about your
    observations! :)

    Surely when dealing with files, 1MB generally refers to 1,048,576
    bytes? And since the OP refered to a file, that would apply in this
    case.

    But anyways, this whole argument has been done to death many times
    before so should we just cut & paste from another thread?
     
    , Apr 16, 2006
    #12
  13. Philip

    Jerry Guest

    wrote:

    > Surely when dealing with files, 1MB generally refers to 1,048,576
    > bytes? And since the OP refered to a file, that would apply in this
    > case.


    There is no reason for a file to be measured in any numbering system
    other than decimal. I know that Microsoft provides such a number, but I
    can't for the life of me see any practical use for it.

    I create a text file and type in *the quick brown fox jumps over a lazy
    dog.* That is 42 characters. I now type it in 39 more times, no space
    or return after the full stop (actually I cut and paste, but for the
    example I type it out, OK?). I now have 1680 (42x40) characters in this
    file. I can print the file, and count the characters, and there are
    exactly 1680 of them. To convert to kilocharacters just move a decimal
    point - I have 1.68 kilocharacters. You can do this with liters of
    petrol, kilograms of butter, anything you like. Noone can give me a
    reasonable reason to convert 1.68K to 1.64K, there just isn't any
    logical reason to do so, except that Microsoft does it.

    The terms Kilo and Meg are abbreviations anyway. If something costs
    megabucks it isn't exactly a multiple of 1,000,000 or 1,048,576.

    The mibi stuff is never going to be accepted, it just complicates a term
    that was used in the first place to simplify things. It's sort of like
    the term Ms didn't solve anything related to the title of women. You
    know have women who want you to know they are married (Mrs), Women who
    want you to know they are single (Miss) and women who don't want you to
    know (Ms). Men still have just one title.

    If you just realize that a K is somewhere around 1000, and a Meg is
    somewhere around a million it's ok. They aren't supposed to be exact terms.
     
    Jerry, Apr 16, 2006
    #13
  14. Philip

    Matty F Guest

    Jerry wrote:

    > wrote:
    >
    >> Surely when dealing with files, 1MB generally refers to 1,048,576
    >> bytes? And since the OP refered to a file, that would apply in this
    >> case.

    >
    >
    > There is no reason for a file to be measured in any numbering system
    > other than decimal. I know that Microsoft provides such a number, but I
    > can't for the life of me see any practical use for it.


    I think it's time we got rid of the non-decimal measure for
    kilobyte and megabyte. They should be 1000 and 1,000,000 only.

    Unfortunately dictionaries such as dictionary.com allow both options:

    kilobyte
    1. A unit of computer memory or data storage capacity equal
    to 1,024 (2^10) bytes.
    2. One thousand bytes.

    megabyte
    1. A unit of computer memory or data storage capacity equal
    to 1,048,576 (2^20) bytes.
    2. One million bytes.

    The first computer I used was an NCR 315, which was a decimal
    machine. It had exactly 10,000 12 bit words.
     
    Matty F, Apr 16, 2006
    #14
  15. In <4441cfe5$> Jerry wrote:
    > wrote:
    >
    >> Surely when dealing with files, 1MB generally refers to 1,048,576
    >> bytes? And since the OP refered to a file, that would apply in this
    >> case.

    >
    > There is no reason for a file to be measured in any numbering system
    > other than decimal. I know that Microsoft provides such a number, but
    > I can't for the life of me see any practical use for it.


    I can't remember how it's presented in Windows, but the Mac Finder shows
    file sizes like this:

    size: 4KB on disk (320 bytes)

    The 4KB is of course meant to be 4kiB (4096 bytes), not 4000 bytes. The
    reason they do this is that pretty much every storage device used on
    computers today stores data in blocks of 512 bytes. The operating system
    often groups those in larger clusters. On my hard drive the cluster size
    is 4096 bytes, so every file takes a multiple of 4096 bytes of storage
    space.

    Because the hard drive, memory, operating system and applications
    normally all move data around in binary multiples it was just natural
    for sizes to be reported in binary multiples.

    You can of course make the argument that the end user should never be
    concerned about the space a file takes, but my first computer had a
    storage capacity of 140kiB per disk, or 280 blocks of 512 bytes each.
    When trying to squeeze as much onto a disk as possible it was important
    to know that adding just one more byte to a file could use another whole
    block (0.5kiB) on the disk.

    Now that storage capacity has increased to the point that the cluster
    size is a tiny fraction of the capacity of most storage devices it
    generally doesn't matter anymore though. Who cares about a few extra
    kibibytes used on a multi-gibibyte disk?

    --
    Roger Johnstone, Invercargill, New Zealand
    http://roger.geek.nz/
    ________________________________________________________________________
    No Silicon Heaven? Preposterous! Where would all the calculators go?

    Kryten, from the Red Dwarf episode "The Last Day"
     
    Roger Johnstone, Apr 16, 2006
    #15
  16. Philip

    MarkH Guest

    Jerry <> wrote in news:4441cfe5$:

    > wrote:
    >
    >> Surely when dealing with files, 1MB generally refers to 1,048,576
    >> bytes? And since the OP refered to a file, that would apply in this
    >> case.

    >
    > There is no reason for a file to be measured in any numbering system
    > other than decimal. I know that Microsoft provides such a number, but
    > I can't for the life of me see any practical use for it.
    >
    > I create a text file and type in *the quick brown fox jumps over a
    > lazy dog.* That is 42 characters. I now type it in 39 more times, no
    > space or return after the full stop (actually I cut and paste, but for
    > the example I type it out, OK?). I now have 1680 (42x40) characters
    > in this file. I can print the file, and count the characters, and
    > there are exactly 1680 of them. To convert to kilocharacters just
    > move a decimal point - I have 1.68 kilocharacters. You can do this
    > with liters of petrol, kilograms of butter, anything you like. Noone
    > can give me a reasonable reason to convert 1.68K to 1.64K, there just
    > isn't any logical reason to do so, except that Microsoft does it.
    >
    > The terms Kilo and Meg are abbreviations anyway. If something costs
    > megabucks it isn't exactly a multiple of 1,000,000 or 1,048,576.
    >
    > The mibi stuff is never going to be accepted, it just complicates a
    > term that was used in the first place to simplify things. It's sort
    > of like the term Ms didn't solve anything related to the title of
    > women. You know have women who want you to know they are married
    > (Mrs), Women who want you to know they are single (Miss) and women who
    > don't want you to know (Ms). Men still have just one title.
    >
    > If you just realize that a K is somewhere around 1000, and a Meg is
    > somewhere around a million it's ok. They aren't supposed to be exact
    > terms.


    K and M ARE exact terms. According to Si definitions K = 1000 and M =
    1000000. In computing terms there is an alternative definition that is
    commonly used with bytes which is similar but KB=2^10 Bytes and MB=2^20
    Bytes - which are also exact numbers. 2^10 is not an approximate number
    meaning around a thousand or so, it is exactly 1024.

    I see little point about being pedantic about K and M not being used for
    binary versions (2^10, 2^20) instead of decimal (10^3, 10^6) when you
    are not exactly pedantic about your use of the English language. i.e.
    there is no such word as "noone" - you mean "no one", you used "know"
    when you meant "now", unless you are American the word is "litres" - not
    "liters"

    Also, your example of "megabucks" is a poor one, that is just slang for
    expensive and can mean a couple of hundred dollars or billions of
    dollars.

    --
    Mark Heyes (New Zealand)
    See my pics at www.gigatech.co.nz (last updated 5-September-05)
    "The person on the other side was a young woman. Very obviously a
    young woman. There was no possible way she could have been mistaken
    for a young man in any language, especially Braille."
    Maskerade
     
    MarkH, Apr 16, 2006
    #16
  17. Philip

    MarkH Guest

    Matty F <> wrote in
    news:hRk0g.13373$:

    > Jerry wrote:
    >
    >> wrote:
    >>
    >>> Surely when dealing with files, 1MB generally refers to 1,048,576
    >>> bytes? And since the OP refered to a file, that would apply in this
    >>> case.

    >>
    >>
    >> There is no reason for a file to be measured in any numbering system
    >> other than decimal. I know that Microsoft provides such a number,
    >> but I can't for the life of me see any practical use for it.

    >
    > I think it's time we got rid of the non-decimal measure for
    > kilobyte and megabyte. They should be 1000 and 1,000,000 only.
    >
    > Unfortunately dictionaries such as dictionary.com allow both options:
    >
    > kilobyte
    > 1. A unit of computer memory or data storage capacity equal
    > to 1,024 (2^10) bytes.
    > 2. One thousand bytes.
    >
    > megabyte
    > 1. A unit of computer memory or data storage capacity equal
    > to 1,048,576 (2^20) bytes.
    > 2. One million bytes.
    >
    > The first computer I used was an NCR 315, which was a decimal
    > machine. It had exactly 10,000 12 bit words.


    Every computer I have ever used (since 1983) have been binary machines.

    The standard SI definition of K, M and G may sound like a simpler thing to
    use, but then my 1GB RAM modules would change to 1.073741824GB RAM modules
    - nowhere near as simple and tidy sounding.



    --
    Mark Heyes (New Zealand)
    See my pics at www.gigatech.co.nz (last updated 5-September-05)
    "The person on the other side was a young woman. Very obviously a
    young woman. There was no possible way she could have been mistaken
    for a young man in any language, especially Braille."
    Maskerade
     
    MarkH, Apr 16, 2006
    #17
  18. Philip

    Jerry Guest

    MarkH wrote:

    >
    > I see little point about being pedantic


    but then you go to considerable lengths to correct my typos.
     
    Jerry, Apr 16, 2006
    #18
  19. Philip

    Jerry Guest

    Matty F wrote:
    > Jerry wrote:
    >
    >> wrote:
    >>
    >>> Surely when dealing with files, 1MB generally refers to 1,048,576
    >>> bytes? And since the OP refered to a file, that would apply in this
    >>> case.

    >>
    >>
    >>
    >> There is no reason for a file to be measured in any numbering system
    >> other than decimal. I know that Microsoft provides such a number, but
    >> I can't for the life of me see any practical use for it.

    >
    >
    > I think it's time we got rid of the non-decimal measure for kilobyte and
    > megabyte. They should be 1000 and 1,000,000 only.
    >
    > Unfortunately dictionaries such as dictionary.com allow both options:
    >
    > kilobyte
    > 1. A unit of computer memory or data storage capacity equal to 1,024
    > (2^10) bytes.
    > 2. One thousand bytes.
    >
    > megabyte
    > 1. A unit of computer memory or data storage capacity equal to
    > 1,048,576 (2^20) bytes.
    > 2. One million bytes.
    >
    > The first computer I used was an NCR 315, which was a decimal machine.
    > It had exactly 10,000 12 bit words.


    Indeed they do, and they will despite what we say here. Can anyone say
    what is improved, or clarified with the use of base 2 meanings of Kilo,
    Mega and Giga? We know that a gigabyte of RAM is always going to be
    exactly 1,073,741,824 bytes, where an 80 GB hard drive will have
    something over 80,000,000,000 bytes. What difference does it make
    really? Why was it found necessary to invent a complex numbering system?

    At least it isn't using 4 decimal numbers between 0 and 255 to represent
    a 32 bit binary number :p Someone thought this would be easier than
    expressing IP addresses in hexadecimal I guess.
     
    Jerry, Apr 16, 2006
    #19
  20. Philip

    MarkH Guest

    Jerry <> wrote in news:4441eef3$:

    > MarkH wrote:
    >
    >>
    >> I see little point about being pedantic

    >
    > but then you go to considerable lengths to correct my typos.


    The whoosh sound you heard while reading my post was my point whizzing past
    your head.

    In case you care here it is again:
    Why be so pedantic about whether KB is equal to 1000 or 1024 bytes when you
    care so little about whether the words you use even exist. i.e. I am
    pointing out the hypocrisy of your pedantry.

    Of course that was what the rest of the sentence that you snipped said,
    interesting how you can take issue with half of a sentence.


    --
    Mark Heyes (New Zealand)
    See my pics at www.gigatech.co.nz (last updated 5-September-05)
    "The person on the other side was a young woman. Very obviously a
    young woman. There was no possible way she could have been mistaken
    for a young man in any language, especially Braille."
    Maskerade
     
    MarkH, Apr 16, 2006
    #20
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