firewire speed vs processor speed

Discussion in 'Buying Tips and Advice' started by mufngruf, Apr 6, 2009.

  1. mufngruf macrumors member

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    #1
    It occurred to me during the lengthy and most helpful thread that I started about purchasing a new computer for my son (intel or not intel...") just how blissfully ignorant I actually am.
    If the new computer has a woefully small hard drive, as in a mac mini for example and therefore is dependent on retrieving information from an external firewire drive, is the speed of the mini compromised by the speed of data transfer from the external drive.. and how much difference does the 400/800 division make?
    or do they all have nothing to do with one another.

    After all, there's little point in buying a Ferrari if the speed limit is 75mph.
     
  2. kastenbrust macrumors 68030

    kastenbrust

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    #2
    You basically want to know if the data trasfer rates from a firewire external hard drive are slower than the data rates from an internal one? Theres two factors at play here.

    1) hard drive read/write speeds (this depends on which hard drive you buy, but its not important at the moment)

    2) data transfer rates

    FW400 transfers at max 393 MB/s
    FW800 transfers at max 786 MB/s

    Internal sata transfers at 150 to 300 MB/s

    So actually a firewire drive is faster, however in the real world it doesn't work like this, and you tend to find the internal sata hard drive works about the same speed as an external FW800 drive.

    http://forums.macrumors.com/showthread.php?t=424621
     
  3. sammich macrumors 601

    sammich

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    #3
    Corrected a few mistakes

    Those numbers above only point to how fast that particular connection goes. The actual speed is determined by the drive that is connected. A Mac Mini for example is connected via SATA2 (300 MB/s), but the hard drive inside the Mini is a slower laptop variety and thus is already limited to around 20-40 MB/s in actual usage. So if you're connecting an external FW drive that's a faster desktop variety, it will reach around the 40-80 MB/s area.

    Bottom line: if you buy a decent external FW enclosure, chances are that it will have BOTH FW400 and FW800.
     
  4. kastenbrust macrumors 68030

    kastenbrust

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    #4
    Thats true but i think you've got confused between Megabit and Megabyte. Check Wiki to confirm my numbers.
     
  5. sammich macrumors 601

    sammich

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    #5
    I think you need to have another look http://en.wikipedia.org/wiki/Serial_ATA

    Think about it...an external connection rivals an internal connection? It's like saying that RAM is faster than on-die cache (that sounded less nerdy in my head :)). Why is every single drive in a pro station like the MP using SATA connections rather than internal FW?
     
  6. BlizzardBomb macrumors 68030

    BlizzardBomb

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    #6
    I can never trust someone who says that ;):p
     
  7. sammich macrumors 601

    sammich

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    #7
    Btw, to answer the OP's other question:

    Computers made in the last few years are more than powerful enough to handle FW800. It just depends on what do with it. The typical user will never find the limitation in FW800 on any new computer.
     
  8. mufngruf thread starter macrumors member

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    Apr 3, 2009
    #8
    Now cut that squabbling... or I'll come upstairs with the belt.

    I'm still not clear (surprise) but I guess that I didn't ask the question right..... I'll retry.
    I am assured that either an imac intel core 2 duo or a mac mini will be much faster than my current setup (dual 1GHZ G4), but if I'm asking it to do things that cause it to have to use data from a firewire external, will it still be as fast.
    For example.. if I want to convert an avi file to an mpeg and the file is on the external drive, will the rate of access (limited by the firewire) cause the processor to be unable to access the file fast enough to use it's speed - or would I be better off to transfer the file to the internal drive first?
    And secondly, if the minimac only uses a laptop drive, what's the biggest/fastest drive that it will reasonably accommodate?

    and I thank you, as always, for your help.
     
  9. deltaiscain macrumors regular

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    Jul 24, 2008
    #9
    Shouldn't it be a small b, instead of a large one? B stands for Byte, and b stands for bit. Correct me if I'm wrong please.
     
  10. sammich macrumors 601

    sammich

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    #10
    The largest laptop drive is 500gig, there are threads on this forum which will help about that if you search (sorry i'm feeling a little lazy to link atm).

    But as I said before: under typical usage, or just about any usage, no one will find the FW400 or even the FW800 with a decent 7200rpm drive inside a limitation. Video conversions are very low data rate since it doesn't happen very fast.

    'B' is for byte, b is for bits. I wrote it 'bit' in full for clarity and helps differentiate for those who will get it muddled up.
     
  11. illegallydead macrumors 6502a

    illegallydead

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    #11
    You are right. Few people care to make the distinction, and especially hardware manufacturers don't care to. I think we can all agree that yes, SATA is way faster than Firewire, contrary to what kastenbrust seems to think.

    And yes OP, you will notice a bit of a slow-down using either method. However, it is not that hugely noticeable in any other uses than a transfer-intensive situation like you mentioned. Overall the best option is to upgrade the internal drive, which on a Mini is a pain in the @$$ because of the case, but will be well worth it. A good 7200RPM hard drive with a large cache will be plenty speedy (not as fast as a 3.5" desktop hard drive, but Apple limits you in that regard due to size restraints)
     
  12. gnasher729 macrumors P6

    gnasher729

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    #12
    Oh my god no no no.
    FW400 transfers at max. 400 Megabit per second. 400 Megabit per second is exactly 50 Megabyte = 50 Million byte per second (real Megabytes, not the MiBs that the OS will transfer sometimes). FW800 is twice the speed. Internal SATA transfers 1500 or 3000 Megabit per second, but two out of every ten bits are not used for data, so the actual transfer rate is 150 or 300 MB/s.

    However, that is not how fast your hard drive works. This is only how fast it can send data between hard drive and computer. In reality, read speed is typically between 40 and 80 MB per second for large files and much, much less for small files.

    In reality, it is very unlikely that your son will ever care about the speed of an external drive, unless he is doing movie editing and in that case you wouldn't buy a MacMini. Any large USB hard drive will do just fine.

    There is no external hard drive for sale anywhere that would be slow enough to slow down video encoding. Raw DVD material is less than two Megabyte per second. AVI would likely be compressed and therefore smaller. The slowest USB drive will easily do 30 Megabyte per second, that is fifteen times as much. You can do video compression over a good wireless network if you have to. That's why I said: The only thing that you can't do with a USB drive is high-end video editing, and you wouldn't do that with a MacMini anyway.

    I tend to always write "Byte" or "Bit". There are just too many people who are careless, clueless or both and get confused otherwise.
     
  13. Consultant macrumors G5

    Consultant

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    #13
    Encoding a movie is processor dependent. Way slower than transfer speed of the drive.

    Firewire has its own processor chip (why it cost more than USB) so not impacted by processor load.
     
  14. Abstract macrumors Penryn

    Abstract

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    #14
    That's my answer, although to be honest, I'm not 100% clear on what he's asking.


    If you're worried about video encoding, then I don't think it matters much. Encoding is slow, even on fast desktops. FW speeds should be fast enough to keep up so that you don't notice. However, if you used an external USB harddrive instead, then problem is that the entire system is slowed down. This is why USB is "teh suck". By using FW, encoding speeds shouldn't slow down because it has its own chipset, and consequently, doesn't affect CPU speed. The FW chipset in a MacBook Pro (and possibly the Mac Mini) isn't great, but it's not going to slow down your encoding speeds like if you were using USB.

    Hope that answers your question.
     

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